Hi all,
I find it foolish to rely on plants to help improve the water quality. Water change is the single most important factor on water quality in a close environment like an aquarium.
Don't get me wrong, it isn't an "either/or" situation and although I only keep planted tanks I'm a fanatical water changer as well. I also like two filters on all my tanks (usually 2nd hand Eheims) for "belt and braces".
Given the choice I would always have a planted over-tank "wet & dry" trickle filter, they are the gold standard of biological filtration because of their resilience if you have a power failure and their large gas exchange surface.
A combination of water changes and plants can help to give you very high quality water, but if the choice was plants or water changes (unless we are talking about a "fail-safe" drip through system with several complete turn-overs of water over 24 hours and an extremely large water reservoir) I would always choose plants.
One reason for this is that plants give you "negative feedback", if you have high levels of macro-nutrients, say from a fish death, plants will take up the NH4+ before it ever enters microbial biological filtration. Because I can't always get at all the tanks (some are in the lab. and I'm away on field work etc) I need a system which can function without intervention for 2 -3 weeks.
If you are interested in water changes in low tech planted tanks there is an interesting discussion in these threads: <
http://www.ukaps.org/forum/threads/fish-health-in-relation-to-no-water-changes-in-low-tech-tanks.28095/> & <
http://www.ukaps.org/forum/threads/low-tech-no-waterchanges.10101/>
A planted system (with emergent and floating plants with access to aerial CO2 and O2), with a trickle filter, will have the capacity to deal with about x10 the bioload of a microbe alone system (like a canister filter).
If any-one is interested in this area I'd recommend "Aquatic phytoremediation: novel insights in tropical and subtropical regions:" <
http://pac.iupac.org/publications/pac/pdf/2010/pdf/8201x0027.pdf>.
L46 pleco lives in a depth of around 25m where there is no aquatic plant. I also breed Apistos, and those tanks have plants as most Apistos live among leave litters
Point taken, I also have
Apistogramma (in fact I think we are both long term members of
Apistogramma forums?), and again I keep all of those in planted tanks with added leaf litter, even if they come from "black water" with no aquatic plants.
I'm not really bothered about whether the fish come from biotopes without plants etc. I would always have plants (even if they aren't physically in the tank), because not having plants is like playing cards with all the picture cards taken out of your hand.
cheers Darrel