Rainbow sharks are freshwater, bottom-dwelling fish that grow about 6 inches long in a home aquarium. They have blackish-green bodies accentuated by red fins. The fish are easy to keep in captivity, but are extraordinarily difficult to breed because of their intolerance of each other and territorial natures. Breeding rainbow sharks involves a large tank (75 gallons minimum) and some patience. You should have prior experience with rainbow sharks and understand that the chances for successful tank breeding is very slim.
Fill a 75-gallon tank with freshwater and layer the bottom with about 2 inches of aquarium gravel.
Add liquid dechlorinator to the tank. This product is available at virtually any pet shop and removes harmful chemicals from tap water. The proper dosage will be on the packaging.
Place rocks and decor around the tank, providing plenty of hiding places for the rainbow sharks, as they are territorial and one may need to seek shelter from the other.
Install the filter. The filter should be appropriate for filtering water in aquariums up to 75 gallons in size. Consult the installation instructions specific to your filter model.
Install the aquarium heater. The heater needs to be adjustable so you can set the temperature. Heaters typically install with suction cups that attach to the interior wall of the aquarium. Set the temperature between 72 F and 80 F.
Power on the filter and allow it to cycle the water for 48 hours to ensure a clean, suitable environment.
Introduce the breeding pair of rainbow sharks. The sharks should be sexed by a professional, as it is difficult to tell for a novice. The male has a black outline along its red anal fin, which the female does not. Both sharks need to be at least 4 inches long to ensure sexual maturity.
Wait one week to see if the rainbow sharks tolerate each other. Attempt to induce breeding if there are no signs of physical damage to either shark after a week. You may need to try another breeding pair if the first two are fighting. Feed the sharks food high in protein, like brine shrimp or tuna, over this time period.
Change 25 percent of the aquarium water using a bucket. This may or may not induce breeding. Continue this practice once a week until you observe mating behavior, whereas the sharks will rub against each other. The female will eventually scatter eggs on the aquarium gravel and the male will fertilize them with a milt spray.
Set up the fry tank. It should be 10 gallons with dechlorinated water and a mini heater. Use an air stone attached to an air pump via airline tubing to circulate the water.
Transfer the eggs to the fry tank using the nylon net. The eggs should hatch after several days, revealing fry (baby sharks). They will feed off their yolk sacs for several days.
Feed the fry liquid fry food after their yolk sacs have been depleted. Continue this feeding for a week to two weeks, then introduce them to baby brine shrimp. The sharks should be moved to their own tanks when they reach 1/2 to 1 inch long.