Fish Department Training Manual


This is designed for retail stores but remain true for fish keeping of all sorts and this is the guideline we use at Twisted Tailfins. Out of all of the animals kept as pets, those kept in aquaria present unique challenges and requirements. Whether or not the keeper is aware, all aspects of the aquatic environment are directly under his
or her control. Fortunately, these challenges can be easily overcome with only a little bit of understanding, thought, and attention. Success in the retail fish department can be broken down into three steps,
each of which builds on the last.

STEP ONE is learning the basics of controlling water quality. Without this, it is impossible to be able to reliably keep an environment in which fish can survive.
STEP TWO is understanding the fish so that you can adjust the water conditions and
stocking to allow the fish to thrive.
STEP THREE is being able to engage the customer and pass on this information so that their experience is positive – not only motivate them to continue in the aquarium hobby, but also to encourage them to return to your store and become faithful, long time customers.

By utilizing these few basic steps, you will be able to not only set up and maintain a healthy and thriving aquatics system, but you will also be able to guide others to do the same. You will be viewed as a credible and reliable source of information for your customers and will set yourself up to form long term relationships with your customers.

Step One – Water S

The fundamental starting point for any aquarium, from small betta bowls to giant commercial systems, is the water. Because they are kept in closed systems, the keeper is responsible for maintaining complete control over the quality of the fish’s environment. While a dog, hamster, or bird will have a constant supply of fresh air being replenished by the environment, the only source of fresh water in an aquarium comes from the keeper. There is no mechanism for controlling the build up of fish waste and toxic
material outside of what the aquarist provides. While it is not difficult to provide a suitable environment for your fish, it does require a modicum of knowledge and attention to be successful.

Nitrogen Cycle

The first and most important step in providing a suitable environment for fish is having a basic understanding of the Nitrogen Cycle, which is simply a fancy name for how fish waste is broken down. While
it is possible to over-complicate this, it a fairly simple process that can be easily understood and explained to customers. Put simply, any organic waste, such as biological waste excreted from fish or the rotting of
dead plants and animals, is released as Ammonia, which is highly toxic to aquatic animals. Beneficial bacteria, which create colonies in your filter and gravel, convert the toxic Ammonia into equally toxic Nitrite.
A second type of beneficial bacteria will convert this Nitrite into Nitrate, which is harmless in low concentrations. Keep in mind that excess nitrate will still cause health problems and is a food source for nuisance
algae. Fortunately, it is easy to control the concentration of Nitrate through regular partial water changes.

Gravel in Aquaria

While it is possible to keep an aquarium with no substrate, gravel plays several important roles in the aquarium including providing area upon which beneficial bacteria can colonize, allowing waste to settle out of sight, and adding to the visual appeal to the tank. When setting up a tank, aim for between one and two inches of gravel. A good estimate for this is to use approximately one pound of gravel per gallon of water in the tank.


People refer to the initial start-up phase of an aquarium as “Cycling” the aquarium. This simply refers to allowing the beneficial bacteria a chance to establish colonies of sufficient size to handle the bio-load of the tank (how much waste the fish will produce). It is easy to track where in the cycle a tank is through basic water testing. The first thing you will see is a rise in the ammonia level. As the first set of beneficial bacteria start to take hold, the ammonia level drops and the nitrite levels rise. The second set of bacteria then develop which causes the nitrites to fall and the nitrates to rise. Once the ammonia and nitrite levels reach zero again, the tank has been fully cycled and is ready for more fish. Keep in mind, though, that it is possible to overload what your bacteria colony can handle. If you add too many fish at once, you may have to wait for another cycle to occur in order to grow enough bacteria to handle the new bioload.


The pH of a tank is a measurement of how acidic the water is. pH is measured on a scale of 0 to 14, with 7 being considered neutral. Anything with a pH below 7 is considered to be acidic, while anything with a pH above 7 is considered to be alkaline (also referred to as “basic”). For most freshwater fish, a neutral pH of around 7 should be a safe range for them to live, though some fish may need a slightly higher or lower pH in order to show their best colors and behaviors or in order to stimulate breeding behavior. The biggest exception to this is found in the African Cichlids, which require a significantly higher pH of between 8.2 and 8.8 in order to truly thrive. For a commercial system, as long as your pH remains stable and doesn’t approach the extremes (i.e lower than 6.5 or higher than 8.0), most common aquarium fish will do just fine. It is important to understand that most freshwater fish, having been tank or farm raised for generations, are fairly adaptable to different pH levels.


Total Dissolved Solids (TDS) is a measurement of all of the inorganic matter dissolved in the water such as Calcium, Magnesium, Sodium, Iron, and other minerals present in the water. While many aquarists take water hardness into consideration, TDS is often a more complete measurement which gives better insight into the condition of the water. Hardness only takes into account Calcium, Magnesium, and Carbonate, while TDS includes that and more. TDS can be easily adjusted through the use of aquarium salt. You can simply add aquarium salt in order to raise the TDS or perform a partial water change with fresh, low TDS water (such as RO water) in order to drop the TDS level. In addition to taking the taking TDS into consideration when looking at keeping fish in an aquarium (you should try to not keep high TDS loving fish in low TDS water, and vice versa), it is also a good idea to take the change in TDS into account when acclimating fish into new water to avoid shocking the fish with a large change. In a commercial system, TDS levels have an enormous impact on fish health and disease prevention. Salt is a powerful disease preventative which when kept at appropriate levels will greatly reduce stress, increase overall fish health, and prevent the incidence or outbreak of disease. See Appendix 5 for recommended TDS levels and more information about testing and regulating TDS. When keeping fish that need water with high pH and high TDS such as African Cichlids, the easiest method of raising these values is to use crushed coral or Aragonite in place of gravel as your substrate. In addition to the normal benefits of gravel, these substances will slowly dissolve, raising the pH and TDS. Even with this method, though, continue to perform water tests, as you may need to also add additional aquarium or Cichlid salts to further raise these values into their ideal range.

Water Testing

In order to stay aware of what is going on inside of the aquarium, water tests should be performed on a regular basis. It is also a good idea to keep a log of all test results in order to always have an easy way to view any substantial changes in water conditions. These water tests should include pH, ammonia, nitrites, nitrates, and TDS and should be performed at least twice a week. We suggest

Water Changes

The main function of a water change is to remove some of the excess nitrate and keep anything else from building up in the water that could be harmful to the fish. In most instances, the amount of water that needs to be changes is relatively small. A good goal for a home aquarium is to change approximately one third of the water each month, although a well stocked commercial system may need 50% or more. This can be done once a month in one large water change, but it is significantly better to do a little bit each week. By breaking the water change up into weekly chunks, you limit swings in water quality and develop stronger routines and habits, ensuring that you don’t let the necessary maintenance slip. In order to change water, you must first drain some water, which is most easily done by use of a siphon hose (Gravel Vac) to drain the water into a buck, sink, or drain. Once the siphon has begun, it will continue draining as long as it is in the water. While siphoning, rummage through the gravel with the end in order to pull out any debris which has settled and may be rotting in the gravel. Once the desired amount has been drained, replace the water with new water treated to remove any chlorine or chloramines. It is best if the new water is also close to the same temperature as the water from the tank, but a slight difference (particularly adding cooler water) should not be harmful.

Step Two – Fish

Put simply, fish are your product and the most important revenue source for an aquatics department. They can keep customers coming back or, if managed poorly, can drive them away. With good water management practices they can be a high markup, high turnover perishable good, but too often live fish are treated as loss leaders used to help sell low-margin dry goods. Good acclimation, husbandry, and handling practices will minimize shrink and keep your margins up. Having a solid product knowledge and the right selection will turn your aquatics department into a profit center.

Water Parameters

One important realization is that all water is not created equally. Temperature, pH, and TDS are all important factors in how successfully a fish can be kept in a given system. While most fish have a fairly wide range of parameters in which they can survive, every fish has a particular sweet spot where it will thrive the most. Outside of this sweet spot, the fish may become less colorful, be more prone to disease, and become impossible to breed. Move too far out of the sweet spot, and eventually the water will become uninhabitable for that fish. Fortunately, though, the range of acceptable (survivable) water quality overlaps for many fish. For most freshwater fish, a pH of anywhere between 6.5 and 7.5 will be habitable. The water temperature in most tanks will be best in the 70’s, with 75-78 being perfect for many fish. There are several notable and important exceptions to these guidelines. Any fish from the African lakes (Malawi, Victoria, or Tanganyika) will require a higher pH and TDS level. Aim for a pH between 8.2 and 8.8 for these fish. Even more commonly, fish in the carp family such as Goldfish and Koi are cold water fish that do best with water temperatures in the 60’s. While some will cool their aquaria for these fish, the average keeper can get away with simply not adding a heater to these tanks.

Stocking Levels

A common question many people will have is how many fish can they fit into their tanks. There are many factors that influence the maximum stocking level including total water volume, filtration capability, and the size of the fish. For small fish, a decent general rule of thumb is one inch of fish per gallon of water. For example, if a person had a 10 gallon tank and wanted to stock it with two inch Platys, a fully stocked tank would have five fish in it (5 fish x 2 inches each = 10 gallons). Alternatively, that person could have two Platys and six one inch tetras (2 fish x 2 inches = 4 gallons, 6 fish x 1 inch = 6 gallons, 6 gallons + 4 gallons = 10 gallons). Unfortunately, this rule of thumb is only a loose guideline. It may in fact be possible to stock more fish than this if using a more powerful filter and keeping up on routine maintenance. Also, larger, heavier body fish need more water per fish because they produce more waste and contribute more pressure to the overall bioload of the aquarium. Goldfish, for example, are much heavier bodied fish than Mollies, even when the same length, and produce much more waste. While you may be able to keep several Mollies in a tank, you probably only want one or two goldfish for that same tank.

Size vs. Stocking Level To illustrate why larger fish need more water per inch than smaller fish, visualize it like this: Take a two inch fish and imagine it is two one-inch blocks joined together. Each one-inch block produces a certain, set amount of waste, so the fish produces two blocks worth of waste. Now imagine a six inch fish made up of the same blocks. Not only is it three times longer, but with the same proportions, it is also three times wider and three times taller, making it six blocks longs, three blocks wide, and three blocks tall, for a total of 54 blocks, and thus produces 54 blocks of waste.

Retail vs. Home Stocking Something to keep in mind, and something which the average novice fish keeper may not understand, is that there is a difference between stocking levels in a retail store where fish are being moved in and out quickly and a home aquarium where the goal is to keep the fish for the duration of its life. A retail store will stock its tanks heavier because A) commercial systems are designed with stronger, more efficient filtration methods and can handle substantial numbers of fish, B) it is more visually attractive to the customer, and C) the fish are not being kept in the tanks long enough for the negative consequences of overstocking to affect the fish.


One of the most common problems among novice fish keepers is determining the amount of food to feed their fish. In the wild, most fish are opportunistic feeders that take advantage of any passing meal they can catch because there is no promise of when the next meal will come along. This is seldom a problem in the home aquarium where meals are steadily supplied by the keeper, yet the instinct to take advantage of any feeding opportunity still guides the fish to eat any food available. This opportunistic behavior is often mistaken as a sign that the fish are still hungry, resulting in the fish being fed too much too often. So how much should fish be fed? This is a question that nobody will agree on, but for a home aquarium a less-is-more approach is often a good idea. Most fish can be successfully kept on a diet of being fed two to three times per week what they will eat within about a minute. In a retail setting, it is important to have a feeding regimen that all staff can easily adhere to. Proper feeding is second only to water quality in maintaining fish health and feeding adequately without compromising water quality is a great tool to fight shrink. Feeding a varied diet comprised of different foods to meet the needs of different types of fish (flakes for surface feeders, sinking food for bottom dwellers, algae wafers for algae eaters) will go a long way to ensure your fish recover from shipping stresses quickly and look their best in your tanks. Ideally, fish feeding will be part of a daily checklist and an assigned task for one of the employees (See sample daily checklist, Appendix 4).

Protecting Water Quality

In order to have the most long-term success with keeping fish, strive to always keep the water quality as high as possible. Even though a well cycled tank should have enough beneficial bacteria to neutralize the amount of ammonia being produced by the fish, you want to avoid stressing the limits of water quality. It is entirely possible for a tank of fish to produce more ammonia than can be broken down, which often is the result of over-fed and over-stocked tanks. Further, even if the tank can break down the ammonia, the result is rapidly rising nitrate, which not only can reach toxic levels of left unchecked, but can also lead to uncontrollable algae problems and drops in pH. Not over-feeding is a key step in protecting your water quality. Limiting the amount of food introduced to the tank limits the amount of ammonia which limits the amount of nitrate produced. It is also vital, especially in the retail setting where tanks are often overstocked in order to be more visually appealing, to constantly be searching for and removing dead fish. Dead fish in a display tank are visually unappealing, diminish the faith of customers that the fish being sold are healthy, and release huge amounts of ammonia as they decompose in the system. Pulling dead fish from your tanks should be done continuously throughout the day, and an assigned task at least 3x daily. Keep track of all dead fish pulled as it can alert you to potential problems before they become widespread.

Schedule of Duties

One of the most important parts of keeping a retail system healthy is developing a set routine of maintenance duties which all employees follow. Everybody should be aware of when the fish get fed so they do not get fed twice. Water changes should be performed regularly and on a schedule to ensure that necessary duties are being completed when they should be. Regular water testing should be performed and recorded at least twice a week to keep track of water parameters and to be able to have an indication if problems should arise. The most important duty from a managerial perspective is assigning these tasks and ensuring that each employee is accountable for his or her assigned task(s).


Once water quality is no longer a problem, the question turns to what fish should be kept, and what can go together. While there are very few rules that apply 100% of the time, there are some general guidelines as to what fish typically work well together. It can be helpful to break all of the fish down into five general groups, though there is some overlapping. See page 11 for generalized fish aggression levels. When stocking a tank, it is also a good idea to consider how fish interact with others of its same type. Some fish, such as Tetras and Corys, do best when kept in large schools. Tiger Barbs, for example, tend to be extremely nippy towards other fish and will constantly harass anything else in the tank if kept in small number, but when kept in schools tend to no longer bother the other fish as much. With schooling fish, you should aim to keep no less than five in a tank, and the more you can keep the better. Some fish, such as livebearers, Angelfish, Rams, and Gouramis, do best when kept in small groups of two to four. Angelfish, for example, will often form pairs when they mature. Once a pair of Angels has decided to try to breed, they will chase away and attack any other fish that comes near their territory. Rams do best in small harems, with one male and few females, due to the male’s tendency to chase around the females in courtship. Finally, some fish, such as many cichlids, do not necessarily need other fish of the same type in order to be content. These fish are perfectly fine being loners in the tank.

In the retail setting, you will usually be keeping large groups of all of the fish you carry. It is up to you to monitor and determine what best suits your needs. Another important consideration is the availability of appropriate cover (such as artificial plants and caves) which not only adds visual appeal but also helps diffuse aggression. Sensible stocking is important for a number of reasons, including your bottom line. Keeping or selling incompatible fish will lead large losses, unhappy customers, lost sales, and damage to your reputation. Visually check the tanks each day for signs of incompatibility such as frayed fins and excessive chasing or hiding.

Generalized Fish Aggression Levels

Community Fish – Generally small fish such as Tetra, Livebearers (Guppies, Mollies, Platys, Swordtails, Variatus), and small Danios (such as Zebra Danios and Glofish Danios). Also compatible with community fish are Cory catfish, Plecos, certain Barbs (Cherry and Rosy), and Dwarf Gouramis. Also, Betta can frequently be kept with community fish provided you never keep more than one male in a tank. Semi-Aggressive – Most Barbs (particularly Tiger and Tinfoil), most Gouramis, most freshwater “sharks”, Angelfish, Silver Dollars, and most Catfish. Something to keep in mind, though, is that barbs tend to be nippy to slow moving fish with long fins, such as Angelfish. Also, Catfish generally will be okay with other fish provided that they cannot swallow them, and thus are fairly flexible as to which category they can go in, provided they are sized appropriately. However, if a Catfish is large enough to swallow another fish, don’t be surprised if the smaller fish goes missing some day. African Cichlids – By and large all African Cichlids are going to be very aggressive. Couple this with the fact that African Cichlids thrive in water with a significantly higher pH than most other fish, and you can see that it is generally best to keep African Cichlids only with other African Cichlids. South American Cichlids – Fish like Oscars, Jack Dempseys, Red Devils, Green Terrors, and more. Frequently these are the largest common freshwater fish and, as one would expect, also tend to be the most aggressive freshwater fish. Putting smaller, more passive fish with these is only going to result in an expensive snack for your Cichlid. Because they are so large, they produce a lot of waste. They are also often fiercely territorial, so it is best to give a lot of space per fish. Goldfish and Koi – While not particularly aggressive. Goldfish and Koi generally do best only with other Goldfish and Koi, particularly because of their cold water preference. Keep in mind, all Goldfish and Koi get large, and the belief that they only grow to the size of their container is a myth. Even the tiny feeder goldfish can easily grow over a foot long, and Koi commonly grow to two feet or more.

“Swimming Zones”

Another item to take into consideration when trying to stock a tank is where the fish naturally swims in the vertical space of the tank. While a large number of fish are going to mostly swim in the middle areas, there are some fish that prefer swimming at the top or staying near the bottom. Many catfish, such as Cory catfish, are going to typically stay at the bottom of the tank, only occasionally swimming up from the gravel. Hatchet fish, on the other hand, almost exclusive swim near the surface of the tank. By considering this, you can add activity to all parts of the tank.


Because of the closed system nature of aquaria, and the reliance on the keeper for providing all facets of the environment for the fish, one of the most physically stressing, and potentially dangerous, times for a fish comes when moving from one tank to another. In addition to the necessary considerations when physically transporting the fish (i.e. how to supply water and oxygen to the fish when it is not in a tank), you must worry about the change in water chemistry and temperature between tanks. If there is too abrupt a change in it’s environment, a fish can become physically stressed, leading to an increased susceptibility to diseases. These diseases could be present either within the fish or in the new tank, but cause no problems due to being controlled by the fish’s immune system. The stress of the move, though, can weaken the fish’s immune system leading to the disease then taking hold. In the short trip from your store to a customer’s home, the amount of transport and shipping stress should be very minimal. For the fish that you receive at your store, though, it is crucial to minimize the amount of stress during the acclimation process. See Appendix 1 for the safest, most gentle method of acclimating your new fish. Ensure that you have a trained staff member on hand whenever you receive fish. If done improperly, it is highly likely for acclimation to cause fish deaths and health issues. Fortunately, our method contains simple steps which, if done correctly, will drastically reduce your first and second day fish losses.

Handling Fish

As the last step before a fish leaves your store for a customer’s aquarium, netting, handling, and bagging fish for customers is an easily overlooked yet very important process. Make sure that all staff who might be asked to catch fish for customers are trained on proper handling techniques to avoid issues. When netting fish, there exists the potential for damage to the fish’s slime coat, scales, fins, and gills. Be very careful when netting fish in order to ensure your customer receives a healthy fish that will adapt readily to his or her tank. Never ‘pin’ a fish against the sides of the tank or gravel and make sure that the rigid sides of the net never make contact with the fish at all. Minimize the time the fish spend in the net, and carefully transfer the fish from the net to the specimen container or bag. At this point, many fish will attempt to jump if given the opportunity (especially barbs, danios, and some cichlids). You can use your hand, the net, or both to cover the open container until the fish can be safely transferred into its bag and sealed. Expect it to take some practice before you become comfortable with this process, but good netting and bagging procedures will help limit customer returns and create a better overall customer experience.

Appendix 1 – Acclimation

Appendix 2 – TDS Pen Instructions

Appendix 3 – Water Test Result Log

Appendix 4 – Routine Maintenance Log

Appendix 5 – Salt in the Freshwater Aquarium

Stress is the number one reason for disease and fish loss. Many things contribute to fish stress including overcrowding (in the retail environment, this is unavoidable), poor nutrition, netting and capture, shipping, and water quality. Fish have a natural slime coating which inhibits the entry of disease organisms (much like an immune system), acts as a lubricant to aid in movement through the water, and plays an important role in osmoregulation. Basically, the cells of a freshwater fish’s body naturally contain a greater concentration of salt than the surrounding water. The cells try to absorb water molecules in an effort to dilute the salt content and equalize the salt concentration between the cells and the water. However, this is too much water for the fish to absorb, causing the fish to excrete the excess water as urine through the kidneys in order to avoid over hydrating. The fish’s slime coating acts as a natural buffer against this extra hydration, but when stressed, the slime coat diminishes and loses part or all of this protection. Keeping higher salt levels in the water can help reduce this Osmotic Stress. Salt also helps protect against many protozoan parasites, such as Costia, Trichodina, and Chilodonella as well as flukes and other ectoparasites. Most parasites have a much lower concentration of salt in their cells than fish do, so by adding salt to the water, you can reverse the osmotic flow. This causes water to be drawn out of the parasites, dehydrating the organisms. Because fish have even higher salt concentrations, this elevated salt level has no adverse affects on them. The easiest method of monitoring the salt content in your freshwater system is through daily testing with a TDS Pen. Salt concentrations can change as the result of adding water to the system (such as in a water change, which will lower the salt concentration), or as the result of evaporation (which removes water but not salt, raising the salt concentration). Keep a log of these test readings to easily track changes or spot problems before they get out of hand. For your retail system, we recommend keeping the tropical system at 2.5-3.0 PPT and your goldfish system at 4.0 PPT. See Appendix 2 for recommendations for a home aquarium. Note: Your TDS Pen does not read with a decimal point, so these readings will show as 25-30 and 40.