I have a 75 gallon tank with an Eheim Classis 2213 filter. The filter gets quite a work out with all the plant debris, and I have an extra Marineland Emperor 400 I can throw on to help out. However, my home doesn't have many outlets, and the only spot I have on my power bar/timer, is for 12 hours a day.
Is the bacteria going to go bad and harm the fish if the filter is only on for 12 hours a day?
Your not going to harm the fish at first it would be wise to use only mechanical media for removing debris. Then make sure you clean it often so as to prevent the stuff you remove from rotting and then putting that material back in the aquarium. If I were you I wouldn't try it at all because you run the risk of your filter not starting back up and burning the motor. I just wouldn't do it. Your best bet is to get a better filter if you can. Until then do an extra water change. BTW you will never get a beneficial bacteria colony going at all that way.
I figured the Emperor would never colonize right, but it would be nice to take some of the load off the canister by getting some of the particulate course matter out. It's pretty hard on the Eheim. I can't remember if it is a 2213 or 2215, but with how bad it gets I think it might be the smaller one. Now that school is finishing up for the summer I can commit more to weekly water changes. Thanks.
Why not upgrade the canister filter? It's quite undersized for a tank that big, despite what Eheim might claim on the packaging. I would use at least a 2217 and even then it's probably not big enough.
Leaving the filter off for 12 hours a day is asking for trouble. Can't you just use a splitter to open up another outlet? I can't imagine that extra filter will pull enough wattage to worry about tripping the breaker.
Power Filter on a Timer 
Linear Mode
