Hi all,
You do not want to do weekly water changes, that's part of the method for non CO2, avoid them.
I haven't tried limited water changes since the 1970's, when "aged water" had all sorts of magical properties and I used to kill all my fish with depressing regularity. I'd need a lot of persuading that it would work for me, although I know Tom (plantbrain) has used it successfully <
Low tech - no waterchanges? | UK Aquatic Plant Society>.
I maybe differ from every-one else in that I want my plants to grow slowly. The problem I have, even with a sand substrate and very minimal fertilisation is that over time the plants tend to fill in the complete volume of the tank, leaving very little swimming room. I don't think the fish mind, in fact I'm sure they don't, but eventually there has to be some intervention.
I think
slowly is really the important word in all of this, I want the plants growing, but as long as the plants are in active growth, I don't mind how slow that growth is.
If my plants are growing slowly I know the nutrient status of the tanks is pretty low, but that all essential nutrients are available at some level. I can use the plant mass and health to both estimate and control nutrient levels.
I started using this approach on the later stages of landfill leachate re-mediation, where you are still dealing with "water" with a huge BOD. As long as you add enough oxygen, and have enough plants, these plant/microbe biological filtration systems have huge biological filtration capacity whilst being extremely resilient and flexible.
From there it is a short conceptual leap to if you start with pretty clean water you can maintain that water quality in exactly the same manner.
There are obvious limitations to this approach, I can't grow carpets, eventually the bottoms of all the tanks are dark and interesting places filled with leaf litter, bits of wood,
Bolbitis, strands of moss and the dangling roots of
Anubias etc.
I always have a wide range of some algae, I look a this as a plus, but I've never suffered from an algae "out-break", and I don't take any special measures to remove, or control, it.
Additionally I often don't know how many fish I have, to the extent that I failed to see any
Corydoras hastatus for several months in one tank, and decided they had probably died. Eventually I had to take the tank down whilst some new windows were fitted in the lab. I added some other small
Corydoras catfish and quite a lot various sized
C. hastatus re-appeared having bred in the mean time.
cheers Darrel