problems with canister filters

[new2salt2]

i have heard that canister filters were bad for a tank. Alos that all a good salt tank needs is a good skimmer and live rock to survive. welll i bought a canister filter at the pet store casue they said it would be needed in a fish tank. (50 gal slat tank here). 20 days later i check my nitrites and they are at 0 same with amonia, but my nitrate is off the charts. I do a water change and rinse and change bio media in filter. 3 days later amonia spikes up and my nitrate is still off the charts. Well i have gone back to a hang on filter for now and gotten rid of the canister. Only been one day and have not checked water levels yet, but had done another chage of 10 gals when i got rid of my canister . In all 25 gal change in 25 days. anyone ever hear of the canister filters causeing this? is it true witha good skimmer and live rock a filter is not needed in the tanks? My fish all seem fine and very active still. any advise would be helpful.

[JoshS]

Well, I'll admit to being away from the hoby for a few years, but I used to use canister filters all the time. I think your problem is from changing the bio media...you just threw out the bacteria that processes the ammonia and nitrites. You really shouldn't mess with bio media much...an occasional wrinse with tank water is about it. The prefilter and chemical media is what you need to change regularly.

As for nitrates, processing them is a whole different story. This doesn't happen in a canister or hang on type filter, so they just build up in the water. Water changes are the best way to control them. Live rock will control nitrates...depending on your fish load.

I imagine a skimmer combined with an suitable quanity of LR and good circulation within the tank would do quite well. That's the basis of most reef tanks.