Can I keep a rainbow shark in a cold water tank?
That’s not really a cold water tank then, it’s a room temperature tank. Tropical tanks have a heater to constantly sustain a high temperature. In the same way, a cold water tank has a chiller system to consistently keep a low temperature for your fish. That said, this tank is not a good home for a Rainbow Shark. Rainbow Sharks are tropical. 18 degrees is way too cold for them. Even 30 degrees is slightly too warm. The worst thing here is, the temperature of the tank is yo-yo ing too much. This will shock your fish a lot. If you have a heater you could keep the Rainbow Shark provided your tank is big enough (at least a 3 foot wide tank, ideally a 4 foot wide, 55 gallon tank).
