Guppy care largely comes down to water quality and feeding.
- Stocking level. Until you have learned to provide your guppies with optimal water conditions and are observing an effective tank maintenance schedule, follow the rule of thumb for the ratio of guppies to tank volume: one inch of fish per gallon. Over stocking your tank stresses the fish and leads to stunted growth. In Reinhardt’s own study, in a static pond lined with plastic and devoid of plants, it took 1 square foot of surface area to support 1 inch of fish. Adding air stones to the pond allowed support for 4 inches of fish per sq. ft. and stocking the pond at a lesser density than maximum allowed better growth.
According to a scientific study (“Population Control in Guppies,” S Meryl Rose, American Midland Naturalist, Vol. 62, No. 2 (Oct., 1959), pp. 474-481), quoting an earlier study by Breder and Coates (1932), a 5.5-liter aquarium will support a maximum of 9 adult fish. “This was their final number whether they started with one or 50. Once nine had become adult, even though more wore born, no more could survive to adulthood.” They go on to say, “The data presented in the present paper indicate that both the production and survival of guppies decrease as the number of adults increase.”
- Filters. Clean your filters (but do not disinfect them) and clean the glass on your aquariums regularly if you must but leaving algae on them actually helps the water quality by eating unwanted nitrates, but of course water changes do that as well. Filters can be rinsed out in the water you drain from your tanks to avoid killing the bacteria in them. Efficient filters with steady water flow support larger colonies of bacteria, which support larger quantities of fish, which improves your chances of finding superior breeders. Use two filters in tanks 15 gallon and larger. When you clean one, the other continues to provide optimal biological filtration until the cleaned filter’s bacterial colony is fully re-established. If you included a sponge filter in the tank then its bacteria colony isn’t affected if cleaned as described above. Note: Philip Shaddock uses two sponge filters per tank and puts one of them through the washing machine with a little bleach every month.
- Water Changes. Fish waste creates an organic soup teeming with both good and bad bacteria. Adding fresh conditioned water to your tank creates optimum conditions for your guppy’s health, growth and fertility. Consider setting up a holding tank. Water conditioners that claim to neutralize toxic chemicals are not completely effective. Use Seachem Prime water conditioner right in your tanks (it neutralizes toxic ammonia, nitrite and nitrate) until you have the knack of good water quality down pat.
- Food and Feeding. The quality and quantity of the food you feed your fish can have a big impact on water quality. Low quality fish food is hard for the fish to digest and is excreted as waste, which in turns fouls the water. Feeding more food than the fish can eat in 1 or 2 minutes causes the food to either go uneaten or it is passed through the fish partially digested. Food and feeding have the largest impact on water quality.
Fish should be fed a small amount every two to three hours. Wet foods (frozen or live) can be digested easier and quicker than dry foods and can be fed in larger proportions. Do not feed a large quantity at one feeding, thinking you are compensating for missed meals. When a guppy eats more than it can digest right away, it passes the food through its gut largely undigested. It is excreted and fouls the tank.