bs6749
Aquarium Advice Addict
No, the ambient temperature won't change the temperature of the tank that much. What is the temperature of the tank? It should be 72 or above. I'd keep it at 76-80.
Actually, Nitrate really isnt bery harmful, until it gets into the 60's. That dosent mean that you should let it get that high, but if missed a water change, your fish arent doomed. I would not do a 90 percent water change. I would do 2 20 percent water changes. 1 today, and the other tommorow. To much water being taken out will stress the fish out. After you do the 2 water changes, test the water again.