Is it possible to overfilter a tank?

[Boromark]

I am thinking of buying a TetraTec 1200 to my 4' tank to provide more water movement and surface churning. My tank is fully stocked including seven 2-3"Clowns.

Currently I have a TetraTec 700 and an Eheim Ecco and I would replace the Ecco with the new filter. (I also now have an Eheim Aquaball which I added to churn the surface after reading Emma's article in Practical Fishkeeping, but I want to connect this to an external trickle filter after reading about aerobic bacteria in one of the LOL archives. In fact, when reading LOL my learning curve is going exponential and my few remaining brain cells are working flat out - I hope you are insured for mental overload in your readers.)

Anyway, my question is, I've a feeling I read somewhere a while ago that it is possible to overfilter a tank and this reduces vitamins/trace elements or something in the water (???).

So - is it possible to overfilter a tank, or is it the case that more filtration is always better?

Thanks

Mark

[Mad Duff]

I don't think it is possible to over filter a tank especially with loaches in mind.

All of my tanks have filtration that would be adequate on tanks double the size, I think this is always preferable to filtration that is just managing because should a small problem occur a small problem could lead to bigger problems.

[Diana]

More filtration does not remove minerals in the tank, unless you add some special filter media that soften the water.

There is a difference between filtration and water movement.

Filtration consists of mechanical, chemical and biological filtration.

Mechanical filtration: Adding more and more sponges, foam, floss and so on might get excessive if you have so much that it does not get cleaned frequently enough. All that debris is stuck in the water flow, and still rotting in the tank system.

Chemical Filtration: Know your water, and install the proper volume of whatever the tank needs. I run peat moss in several of my tanks, coral sand in some others. I do not run activated carbon except to remove medicines. Purigen is also implicated in mineral removal, but even in high tech, heavily planted tanks it does not seem to be a problem.

Bio logical filtration: Nitrifying bacteria are growing on all the surfaces in the tank, including ceramic or plastic 'bacteria condominiums'. The total population of bacteria, fungi and other microorganisms is limited to their food supply, not to surfaces on which to grow (Unless you have a bare bottom tank, very limited surfaces). Adding more and more places for the bacteria to live does not mean you grow more and more bacteria. The population will be more spread out. If something happens to one part of the population (lets say you over clean a filter and disturb the bacteria) then there is a lot of other places growing bacteria that can tide things over while the disturbed population re-establishes itself.
Live plants in a tank can remove all the minerals, then you need to add macro and micro fertilizers for the plants. Most people would not call this overfiltering, though.

Excess water flow: This is why you are very careful about placement of powerheads, air bubblers, filter inlets and outlets...
You want to be sure there are no dead areas where debris accumulates, and you want just the right amount of water movement for the fish you want to keep. There will be different amounts of water movement in different areas of the tank, and some fish may choose to hang out in the direct path of the flow, or in quieter areas.
In this sense you can have too much water movement. Angels, Discus, Gouramis and some other fish do not like too much water movement. Other fish (most Loaches) prefer more water movement. Some (Hillstream Loaches) require an extreme amount of water movement.
Include the water flow from the filter when you are considering how much water flow a tank has, but do not confuse filtration and water movement.

[Boromark]

Thanks very much for this information, Mad Duff and Diana. I understand the principles behind filtration a lot better.

I think it's best to improve my filtration just to be on the safe side. I realise that water changes are also needed.

I used to run a Hydor Biowheel, which rotates a small sponge pad in and out of the water, and which was advertised to reduce ammonia in the water. So does this mean that with a biggish external trickle filter all of any ammonia created in the tank water would automatically be eaten?

Thanks

Mark