Saltwater filtration

[Myaj]

Okay, I've heard it a million times.

"Cannister filters on saltwater tanks are nitrate factories"

So, is it a really bad idea to put a cannister filter on a saltwater tank? Can I get away with it by changing the media or anything? I don't understand how its any different than a prefilter on a sump or powerhead, or even live rock with current going through it.. so to me, that statement screams "myth".

Reason I'm asking.. Right now on Paris's tank I have a powerhead going with a prefilter, and an AC500 (hang on back power filter, only media is the sponge). When I set up her tank, I was planning on using the overflow/sump and a skimmer, not any filter to hang on it. The AC500 barely fits between the tank and the wall, but I'm noticing moisture and salt creep are starting to damage the wall a bit (paint/plaster cracking and peeling). So I need to get the HOB filter off there (we rent, and I do have to admit the landlord will probably never even notice this additional damage, the walls in here are all old and cracked.. gives it character, right? LOL But I don't want it to start growing mold or anything (had that issue with a brackish tank I ran with the filter too close to the wall).

So.. the issue with the sump is one that I've been dragging my feet on dealing with... I unhooked it after an unfortunate backsiphoning situation that resulted in about 9 gallons of water in our carpet and the downstairs neighbor's apartment , and instead of fixing the issue that caused the backsiphoning, I left it unhooked. The sump has pretty much evaporated out, though ocassionally I add water. I don't know how the heck to re-cycle the sump.. its still full of rubble in one section, a deep sand bed in another, and even a clump of half dead chaeto that I have no idea how it survived this long in what has to be incredibly high salinity.

I can't take the sump out and empty it, because its inside the stand. So it sits, and ocassionally I add more water. I *could* fill it up, adjust the salinity and fishless cycle, but with the various "compartments" I doubt I could get good enough water circulation to cycle it properly. Not to mention there's probably a whole lot of dead "nasties" in there, between pods, chaeto and just gunk in general. Thank god the thing hasn't started to smell bad!

So er yeah, back to the subject, I want to take off the AC500 and hook up the XP3 canister instead. Bad idea?

I'm still trying to figure out a way to use my skimmer on the main tank, its not made to fit over the big lip of a 75. I was going to use it on the sump, but well, that didn't happen...

Buying a new skimmer would be the easy answer

[Dadof4]

I've wondered the same thing myself. I'm bringing my GSP up to marine and I have been told to get rid of my canister filter. I cannot do this because I don't have access to under my stand, everything currently is on the side hence the canister. Why is it not possible to remove the carbon or any chemical filtration and add a load of bio media like bio-balls or ceramic pieces and add a bunch of LR to the tank?

[edmlfc1]

Myaj,
I tell people a sump is better for a sw tank. I know that not may people will take their canister apart once a month and clean it. A canister can be used only if you stay on top of it. If not cleaned on a regular basis, yes, it will become a nitrate factory. Just like if you use a wet/dry (the bio-balls) if not taken care of properly will become a nitrate factory.
I have heard of people using live rock rubble or lava rock rubble in the canister for years and not having a problem. I've never tried either one in a canister. I did use a canister on my fw/bw/sw tank for a while, until I got the wet/dry. I also clean my canisters once a month. Unlike my cousin who cleans her canister once every year or two.
IMO: it depends more on if the person will keep up with regular cleaning or not. Since we don't personally know everyone it's better to suggest a sump, it's easier to take care of and you can hide all your equipment in it. And it won't become a nitrate factory.

[Agnate]

My roommate uses a canister (XP3, I think) on his 75 gallon REEF tank, and his corals are doing well. Like edmlfc1 said, if you don't clean it, it will become a nitrate factory. I think the idea of filling it with live rubble is BRILLIANT! Perfect way to make a "sump" in desperate times.

Not really sure what you'll do about a skimmer, though. I use my HOB octopus skimmer (the single-pump) and it fits quite well. It's a serious pain in the rump to clean, though, as it's HUGE and holds like 2 gallons of water (it's about 3 inches wide x 18 long x 16-18 inches high). It needs to be cleaned on a regular basis, as it starts to act up otherwise... but I think that might be because I have a faulty pump. *Shrug*

[Myaj]

I guess I don't understand how it can be a "nitrate factory".

I mean, the waste is either in the water, or it isn't. Its going to get converted to nitrates.. if its not, its still either ammonia or nitrites, right?

So how can a filter determine how MANY nitrates you have? Is there some way a canister filter magically produces more nitrates than the source of nitrites would provide for? This is where I"m confused.

And how would putting rubble in a canister differ from biomedia??? If that works, I have plenty of rubble.

[Agnate]

As I've understood it, live rock generally contains other organisms that can break down nitrate (not all of the nitrate, of course) into other elements and consume them, and those organisms also consume the various pieces of detritus and waste that float around in the tank. Thus, if you abandon the use of filters and go with a huge amount of live rock, you'll have a large amount of these organisms to break things down (the waste that turns into nitrate, and a small amount of the nitrate itself). However, if you use a canister filter, a large amount of the waste gets trapped in the canister. I'd also wager that the slightly larger organisms (like pods and whatnot) would get trapped in the sponges/floss and end up dying. By having all that waste decomposing in the canister, you'll get a large increase in nitrate.

I'm sure if you cleaned the canister often, you'd be fine. Like I said, my roommate uses one on his reef tank and his corals are growing nicely, so it's not like it will instantly kill your puffers. My guess is that it's just better to have a wide variety of living organisms to handle the waste (coupled with Vitamin C dosing and water changes), rather than relying on HOB and canister filters.

The reason I like the idea of putting rubble in the canister is that you can get all the benefits of the canister (water flow, extra water volume that's out of site, basically-silent operation) without worrying about cleaning it out every 2nd week (since it would be similar to closed-loop system), AND have the benefits of micro-organisms consuming the detritus (since you likely wouldn't have put that rubble in your tank).

[Myaj]

Well the tank has plenty of live rock in it already.

I'm not looking at the filters as filters per say, more for water movement (Paris tends to bang things about so I don't want to add more powerheads). So sounds like the way for me to go would be the XP3 with rubble in the baskets and nothing else. That's easy enough. I just was worried if regular media creates a "nitrate factory" why wouldn't rubble do the same thing.

[Agnate]

Yeah, my guess is that most people are negligent (myself included), so cleaning the canister wouldn't happen all that often on a saltwater tank, and thus you'd have your nitrate factory. At least with live rock, it's somewhat cleaning itself, hehe.

[ryverrat]

Here's an idea we are considering to try- fish.com has a little canister filter that the plastic is almost clear- getting it and setting in the window next to the saltwater tank (only 29g and can't fit a sump under it). We are going to put macro algae in it. This will help reduce the nitrates in the tank ( without it my nitrates have only gotten to 20ppm after 1 1/2 weeks between water changes- have some corals that are doing fine and 30lb of live rock). My goal is to have it remove enough nitrate and phosphates so I don't get the algae growing on the glass. My solandri also loves macro algae- ate ever piece of it in two days the last time I put it in the tank. If it grows I can give the extra to him for a snack.

[Myaj]

Ryverrat, I'd be concerned that the sunlight would grow too much algae (macro or nuisance), the filter itself or the hoses will get plugged up, seals will let loose and your entire tank will be pumped/siphoned out onto the floor.

Worst case scenario of course.

[Idontknow]

Thanks for posting this, Myaj. I was wondering about this myself. I just got a new 200G that came with a canister. I thought it would be a waste not to use it, so I was just going to use it as a prefilter and add live rock, protein skimmer, and a wet/dry. But, if the canister can be used maybe I won't need the wet/dry.

About putting live rock in the canister, would that be the only thing or should their be other media in there as well? If so, what is recommended?

[Myaj]

It sounds like the live rock is all you'd need in there.

Now, I would assume a wet/dry would be a heck of a lot worse on a saltwater tank, as far as a "nitrate factory". But I'm just guessing..

[edmlfc1]

If you use a wet/dry with bio balls or bio media yes, you will still have a nitrate factory. Again, you can put lr in the wet/dry and that makes it better.
Unless you want to clean bio-balls and/or bio-media once a month.

[Idontknow]

Thanks for the advice, everyone! I think using the canister with live rock might be the way to go. I still plan to add live rock and a protein skimmer as well.

Although, I am still not clear on why using a canister with freshwater not be a nitrate factory , if they are not cleaned. Do marine fish produce more waste than freshwater fish? Are the fresh water bacteria more effective than saltwater?

[Dadof4]

Here's another question, would it work if you ran a canister filter with just sponge or LR and sponge and had it empty in to a sump/refugium and use it like a prefilter?