I just added a small school of Ember tetras to my community 23 gallon tank with an aquaclear filter, and two of them died the next morning found stuck in the filter. I checked again the next night and found another one stuck between the sponge and the glass; luckily, I caught it just in time and he survived, swimming happily back in the tank. I turned off the filter for now, but, what do I do? It only seems to happen at night when the aquarium lights are turned off. Can you not keep tetras with powered filters?