Canister filter's???


New member
I've been using a canister filter for 6 month's now and have had alot of problem's with random stuff. Every once in a while I'll get a new coral and it will die. Sometime's. What can a canister filter do that is bad?


New member

Same as what Dave said, the filter itself is great for fresh water where the nitrates aren't a problem. But you need to run it much different for salt water to keep the nitrates out. If possible don't use any type of pads or floss in them. Just use it for holding chemical media and water circulation.

Test all the normal parameters. Ammonia, Nitrates, PH and Calcium at the very least. Are you using well water? municipal water? RO water? If it's municipal water, find out if they use chlorine or chloramines.

Then, what kind of coral and how much light are you running? What else do you have providing water flow to the tank?



New member
i agree with everyone above i have a fluval fx5 that is on my 90 gallon and i have to clean it out every week so i dont have a build up of nitrates. kind of a pain it the you know what. want to go to a sump once i get all the stuff i need. i dont know if it is all your canisters fault though with having problems you have to be a little more specific about what is going on. you can keep a very nice reef that is healthy with a canister it is just alot more work than doing it with a sump!!!!!!! i have a mixed reef with sps lps zoos and some softies and have excellent water quality but like i said every week i have to take it out and clean it and i only run a filter pad in it once a month when i blow out all the rocks and cloud up the tank and the pad is only in there for a couple days then i take it out. other than that i use it for carbon phosban and water circulation


New member
Just make sure you clean it every 2 to 4 weeks. I clean mine as part of the water change every other time.
The only canister filter I have ever owned was for my very first marine tank. I of course cannot for certain say that any of these problems I had are directly related to the tank but here...

My first problem with canister filters is their tendency to have hoses come free/ leak or even back siphon all the water from a tank.

But my major issue was the difficulty of keeping it clean, which slows the circulation, and eventually nitrate can be a major issue.


Reef Monkey
Premium Member
Good suggestions by all, but I'd like to add that you may not want to fixate on the canister filter being the problem (or at least not the only problem). Tell us a little bit more about your tank (how long has it been set up, what are your current water parameters, what type of lighting and filtration do you have, etc.) and what types of corals are you adding. Also, how are you acclimating your corals? Finally, how are they dying? Are they getting white first, is the flesh coming off, are they just slowly wasting away?


New member
As has been said remove pads and media and use it for flow. Occasionally i will run carbon through it but thats all. But as Islandcrow said check all other options as well as the canister may not be the issue.
For the record, I feel compelled to suggest some corrections to what others have posted here. I don't disagree with the intent, but want to make sure the content is correctly understood.

Canister filters don't "put out" or otherwise create nitrate. They are not, on their own, a source of nitrate. There is, however, a common notion in this hobby that they are inherently bad because they can lead to high nitrate levels.

Nitrate in our tanks occurs when other nitrogen-containing substances (mostly ammonia and nitrite) are broken down by nitrifying bacteria. These bacteria are sessile - that is, they find a nook or cranny somewhere in your tank and stay put, spawning generations of relatives. A small piece of sponge or filter floss can hold millions of bacteria - these types of materials are great at providing them with a good environment.

Hence, if you put a canister filter on your tank and fill it with flossy or porous media, then leave it alone, it'll soon colonize and start breaking down biological waste. One of the byproducts of this will be nitrate. This alone isn't a bad thing - nitrate is much less harmful than ammonia, for instance. However, in a sensitive reef tank, nitrate can cause all sorts of problems. Hence, most people would rather not let bacteria break down organic waste - instead, most modern hobbyists attempt to remove the waste completely from the system, through means such as skimming.

Of course, if you remove and replace or rinse off the media in a canister filter often enough, the bacteria will never gain a foothold. In this case, the media can perform as a mechanical filter, trapping and holding waste until you have a chance to remove it. But this would have to be a fairly regular job - as in several times a week - to prevent the media from becoming colonized.

All that said, I'll echo what others have suggested - don't try to blame the canister filter. But, make sure you are using it correctly and understand the implications. Evaluate your entire system, as the cause for your problems could likely be coming from elsewhere.