Filtration. Is it needed?


Prolific Poster
Jan 21, 2007
I was looking at member's planted tank photos elsewhere and noticed many were using canister filters as a means of biological filtration in their heavily planted and lightly populated tanks?
I cannot see any advantage. If anything filters will be competing against plants for NH3/NH4+. I have a 180G forest with small fish load. I have 2 powerheads with large sponges PRIMARILY for mechanical filtration. No canister filter. No NH3.

Where is the logic in using such filters where the emphasis in an tank set up is geared towards plants. At what point would one need to think about adding a filter? Can NH3 measurements be the determining factor in helping one decide
whether filters are needed?



Lifetime Charter Member
Lifetime Member
Nov 21, 2007
Los Angeles, CA
The key here is fish load. With a heavily planted tank, you can get by with little filtering, if your fish load is light. Most of us would rather push the fish load a bit because we enjoy them, though that does require filters of some type.

Filters also give you peace of mind in the sense that if a fish dies (and you do not notice) and decomposes in your tank, it is much less likely that ammonia/nitrites will spike and kill off other critters. Overfeeding, among other things, could also cause problems. There just not as much margin for error in a lightly filtered tank.

I've heard a lot about the "Au Natural" method promoted by Diane Walstead (sp?). I don't know much about it, but it is similar to what you are describing.


Lifetime Charter Member
Lifetime Member
Jan 24, 2005
Sacramento, CA
The higher the light intensity, the more critical it is to keep everything else near perfect, and that includes water cleanliness. El Natural tanks can get along without much filtration, and water quality can vary without much worry about algae, but only because of the low light intensity. But, if you have a really high light intensity and don't use a good filter, kept clean with routine maintenance, algae will soon be knocking on the door!


Lifetime Charter Member
Lifetime Member
Jan 24, 2005
I would say that the main advantage of filtering in a well-planted aquarium is that it causes the water to circulate, thus spreading nutrients around. A submerged water pump would work just as well if not better.

BTW, a decaying fish can be seen as a delayed-release plant nutrient. :)



Guru Class Expert
Feb 17, 2007
Lincoln, UK
Also we assume these days that organic N sources trigger algae and therefore we try to remove amonia and then replace with inorganic sources (KNO3.)

In many of the UK tanks we are using Seachem Purigen in the filter to completely remove ammonia!!!

I ignore the filter for circulation / flow Mine is 700lph on paper which is nearly 6 x turnover of my tank volume per hour but after flow reductions will be nearer 350lph.

I have a Koralia1 for circulation pushing 1500lph with minimal flow reduction. The filter is just there to filter.