Perch are typically game fish that are found in North America (yellow perch) and Europe (European perch). The fish can reach fairly large sizes, topping out around 16-24 inches. They are often very aggressive, making them difficult to keep in an aquarium and therefore are not often kept as pets. However, if you're determined to keep a group of perch in captivity, there are several materials you should consider and steps you should take to keep your fish healthy and happy.
Place the 90-gallon aquarium where it will not be in direct sunlight. This will ensure that it doesn't get too much light, which could result in extraneous algae growth.
Rinse the gravel under fresh water with a nylon fish net to remove any dirt or dust, and then layer it at the bottom of the aquarium. About two inches of gravel should suffice.
Fill the tank with fresh water. In the wild, perch are usually either fresh or brackish (slightly salty). However, it is best to go with fresh water since brackish water can be very hard to maintain. Add liquid dechlorinator to the water to remove any chlorine (the proper dosage will be on the packaging).
Install the aquarium heater and make sure the water stays between 4192 degrees Celsius, as this is the optimal temperature for healthy perch according to the Yellow Perch Culture Guide.
Install the aquarium filter, which should hang on the back of the tank and suck up water using an intake tube then expel the clean water back into the tank via a ramp-like spillway. Let the tank water cycle for at least 48 hours before adding the perch.
Acclimate the perch to the tank water before setting it free in the aquarium. This can be done by adding a cup of water from your tank to the water your perch came. Add a cup every five minutes until you've put in five cups, thus allowing the fish to adjust to the temperature of your tank water. Move the fish over with the nylon net. If the perch comes in a bag (as opposed to a bucket or cooler), float the bag in the aquarium water for 20-25 minutes, and then let it swim free.
Feed the perch a diet of meaty foods like earthworms, tubifex worms, beef heart or feeder goldfish. Perch will eat anything that can fit in their mouths. Use caution when using feeder goldfish, as these can leave dangerous ammonia in the tank.
Change the filter cartridges at least once every two to three weeks and change one quarter of the tank water once a week. This will ensure that the tank water stays clean without eliminating all of the beneficial bacteria.
Weigh down any decor like plants or pieces of wood. Perch are destructive and will uproot plants and knock over decorations.
Perch are naturally aggressive and should be kept alone. Adding other types of fish to the aquarium (or even other perch) may lead to fighting.