Biological filters

[Goblin]

I just set up a 55 gal tank and plan to do the fishless cycling.

I was wondering how much the gravel on the bottom of the tank contributes to the bio filter effect? The amount of rocks in my 2 gallon canister is comparatively small vs the
amount of gravel in my tank.

I can see why undergravels are superior for bio filters.

Will not having a undergravel limit the amount of amonia that the bacteria can consume? or will it limit the total amount of fish a given tank will hold?

Undergravel bio filters should be able to handle a much larger ammonia load (fish load)

I'm thinking you can get away with fewer water changes with undergravel. It pulls all the toxins down away from the fish. Sure they may hold high concentrations under the gravel but the water above should have less ammonia and nitrite than a tank with just a
canister filter for a given period of time.

Is this correct?

 

[KnuckleHead]

Its correct that with under gravel filters the vast majority of the bacteria is housed there. The problem with those filters though becomes quite clear when you need to clean. All that gunk will build up underneath and eventually needs to be removed. That means tearing the tank apart and redoing it over and over again. Doing so also puts a load of stress on the occupants. Yes the filters pull toxins down but it also shoots it back up the uplift tubes. Regular water changes are still required. I would just use the canister filter providing its large enough.

 

[FishDan]

I was wondering how much the gravel on the bottom of the tank contributes to the bio filter effect? The amount of rocks in my 2 gallon canister is comparatively small vs the
amount of gravel in my tank.

The gravel in your tank simply adds surface area for the biological colonies to grow, as the gravel adds some more three dimensional surface area for them to cling to. Gravel is not needed, the colonies will grow just as well on the glass at the bottom of the tank, as they grow on any and all surfaces in your tank.

Will not having a undergravel limit the amount of amonia that the bacteria can consume? or will it limit the total amount of fish a given tank will hold?

No. Many people no longer use UGF and they do not have any problems. I have never used an UGF (of course I am new to the hobby, with only 1.5 years of experience). I use sand in my tanks, so an UGF is not usable anyhow.

Undergravel bio filters should be able to handle a much larger ammonia load (fish load)

UGF will not really matter, and shouldn't be added as an excuse to overstock.

I'm thinking you can get away with fewer water changes with undergravel. It pulls all the toxins down away from the fish. Sure they may hold high concentrations under the gravel but the water above should have less ammonia and nitrite than a tank with just a
canister filter for a given period of time.

Is this correct?

No matter what your filtration, there is no excuse not to do frequent water changes, and a filter of any kind alone will not alter that. The toxins that you talk about being "pulled away" has everything to do with the biological colonies and less to do with the filtering of an UGF (yes, they do allow for additional bio-bugs, but if used in conjunction with another filter it won't be that much difference). The toxins that are held in high concentration under the gravel/in the UGF plates are still in the water, and after a time this "gunk" will start to act as additional bioload, and not help to recuce it. Just because it sits under the gravel or in the UGF plates does not mean it doesn't affect the water.

\Dan

 

[CFC]

Undergravel filters are seriously outdated and have been superseded by internal and external power filters which are far superior in every way, i dont know where you have been getting your information from but it seems to be about 10 years out of date. UGF's were good in their day as they gave a larger surface area for bacteria to colonise than the other filters of their day like air driven box and sponge filters, but came with the problem that the whole tank needed to be stripped down once every year to clean under the filter bed. These days with modern power filters the water is circulated around the aquarium and through the filter at a much faster rate, a good filter will circulate the entire tank 10 times a hour or more. This means more water is placed in contact with the filter media so a smaller surface area of media is required in relation to the size of the tank.

 

[daisycat]

Just to add my personal experience of UGF versus canisters.

We had UGF for about 3-4 years and it was a nightmare...gravel always looked dirty, pain to clean, powerheads kept breaking and were noisy.

Then we got our lovely Fluval canister on the 30g tank and I haven't looked back. It is so easy to deal with and quiet. We have an Eheim canister on our new 105g tank and that is even better than the Fluval in terms of usage etc - but it does cost more.

I wouldn't use UGF again as it is just so labour intensive.