I just got my new AquaClear 300 filter and 150 watt titanium heater for my 29 gallon tank. I have the new filter set up and running next to the old junky Aquascape (nnnnnn) filter which I will eventually remove. My question is how long I should leave both filters going to keep the cycle healthy? My levels are 0 ammonia 0 nitrites just under 40 on Nitrates(I know I know but CANNOT get them down no matter what I have tried). I can already tell the difference in the water clarity even though it has been less than 24 hours. That was the reason I replaced the old one. The water was ALWAYS cloudy no matter how great the levels looked. I also just finally finished getting all of the gravel out of the bottom of the tank. With regards to that, since gravel is supposed to be great at keeping biobugs where do the critters go now??? Are the ones in the filter media enough????

Biobugs grow at a maddening pace! That said, I would consider keeping your old filter in place until it's needed somewhere else. Can't have too much filtration! Or, if your set on giving it up all together, at-least salvage the media in the filter. Recycle it back to your Aqua-Clear. There's tons of room for media in those. I'd wait a while (2-4 weeks) before taking the old filter out entirely. Test tubes will tell you right away if it's too soon to pull the filter completely. Save the filter in a bucket of tank water (running is best). That way, if you show Nitrites, you can slap the filter back on for a bit more. Hope this helps!