I dont believe that extra filter is neccessary

Can I hear an Amen??? I agree with you 100%, no matter the filtration all the shibby still ends up being nitrate in the water and the only way to remove that is with water changes.

I have a 30 gallon with one fat and happy 12 inch piranha and no gravel or plants. This guy eats and produces more waste than a thousand guppies. My filtration? A 10 year old Whisper II. I tuck a piece of quilt batting around the pad to act as a pre-filter and this gets discarded and replaced every 2 months or so. The actual filter pad lasts 6 months or longer before needing replaced. The water sparkles and smells nice and I do not see a need for more filtration than that.

Why increase noise, maintanance and electric usage to spread the bacteria around when it needs such a small area to get the job done?

OK, you are correct that you will wind up with the same amount of nitrifying bacteria regardless of the number of filters you are running (unless, of course, your tank is large enough or heavily stocked enough that it produces enough ammonia to keep two such filters running). And also that more filtration doesn't reduce the amount of water changes you need to do (especially with sensitive species).

That having been said, there are still a few reasons why an extra filter is a good idea:

01. Backup. If one malfunctions, the other is likely to still be running. Result: no crisis or disaster.

02. Starting new tanks. When setting up a new aquarium, you will be able to substantially shorten (some might even say eliminate) the standard cycle time by simply transferring one of your filters over.

03. Staggered maintenance. You can really give one filter a great cleaning, knowing that the other is there to pick up the slack while the first gets back on line, bacterially speaking.

04. Just one more fish. If you see a fish and just have to add it, but put it in a tank with some spare filtration capacity already functioning, the bacterial ramp-up will be almost instantaneous. No crashes.

05. If your "main" filter is an Emperor 400 or 280, or any of the other HOB cartridge filters), using an AC300 or 500 with sponges only will take most of the mechanical filtration load off of the other filter, saving you $$$ in the area of cartridges. Also, the flow on the AC's seems to be a little better at getting the detritus out of the tank, which means that you have a more effective mechanical filtration system in place.

06. If your "main" filter is a canister, then basically the same argument applies, except that instead of saving cartridges you're extending the time between canister cleanings.

So there you have it. Kind of like wearing a belt and suspenders, I guess. To each his (or her) own.

No, I completely agree with you and just figured it was best to get all the debunking and other info into the thread to make it as useful as possible.

Now let's continue adding comments like this for a few days just to keep it at the top of the list and get a bunch of people to read it.

I could put one of those d-mned smilies here, but I don't do (note: not can't, won't) emoticons so everyone will just have to understand that I am posting with the most amiable of intentions.

I, on the other hand, completely disagree that more than one filter is a waste. Of 24 current tanks, zero, zilch, nada has but one filter. Moderate sized tanks have about 3. Large tanks have more.

Certainly you cannot have any more nitrification bacteria than your bioload requires, that is a given. Numerically most of my filters are mechanical only, so set that the keep suspended and capture particulates quite well, and are frequenly and thoroughly rinsed - get the stuff out of the tanks before the heterotrophs and saprophytes break it down. Without multiple filtration I find it quite difficult to keep nitrates below 10ppm, with multiple frequently rinsed mechanicals, it is easy.

http://www.aaquaria.com/aquasource/cannister.shtml

But this is all personal choice, If you are well pleased and content with a single unit, more power to you. But not for me thanks, I like easy care and high water quality. If multiple filters make that easy to me, that is my choice.

Originally posted by ROLLIN
I agree an extra filter is good for those reasons, but I was only talking about how alot of people think it will reduce the need for water changes and maintenance, just those 2 reasons.

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You are correct on this. I use second or third filter for the sake of back up and water current, not because they will reduce nitrate or water change requirement. Too many filters may even increase nitrate if they are not cleaned frequently. Many people were surprised to find that nitrate shoot right back up after water change because they allow their filters, specially canister, to accummulate waste indefinitely. But having to clean too many filters increases the maintenance work. So there is a diminishing return of how many filters is optimum. More is not better.

I personally use two filters on my 55gallon and one on my smaller tanks. I do this for several of the reasons named above, plus I think it's better for turning water over and getting even dispursal of heat and water quality all over the tank. I think 1 filter for every 2 or 3 feet of tank length is probably sufficient to meet my liking. If you don't need so much water turned over, buy smaller sized filters. All this results in peace of mind, cleaner (visibly) tanks usually, and versatility that just can't be gained with one filter.