I'm baffled by the compost as well!
We Dutch are up to our ears in planted tanks, but the use of compost and such is a method wich has gone with the dodo a few decades ago here. Just too many uncontrollable difficulties can happen.
First there's the anaeroob issue Dinyar referred too; he's right about that, it can be risky.
Second; like Jools said; it happens all over the wild. What he probably forgot to say, was that the usual habit of most tropical fish doesn't contain all those nice, little plants at all, just mud, gasses under the mud, and huge swamp plants (weeds and reeds) growing well above the water, if any.
Third, nature has a balance and it's buffered too. A tank hasn't got this, so you need to be in control 24/7!
The best way to do this, is using a much simpler method: just a riversand substrate, you can put a thin layer of peat underneat, if you like to stick to natural, brown acidic water. Peat contains less nutrients than compost, it rarely rots (well conserved, like bogwood!) and stabilizes pH too, wich is good.
Plants that require more than just sand and a bit of peat, can be made to grow by adding a bit of clay. Easiest way is just roll "clay-marbles"; bake them just a bit in an ordinary oven (to avoid getting a mess, when handling them in the tank!), and put one or two near the place, where such a plant is planted (Echinodorus, Lotus, Aponogeton, Crinum etc like this).
South American plantsa need quite a bit of Ferro (iron). a very old recipe that really works is burying a rusty nail near the tankfloor! Make sure it's blunted, in case of digging catfish. Jools can probably agree, there's a load of little brooks in Amazonia that are brickred because of the iron. C aeneus for example has a natural habitat like that, if I'm correct.
Fourth, the best way of having a healthy plant growth is using the right amount of light, and lots of it. The sheer amount of light on equatorial rainforests is baffling!
Especially pale people need a good sunblock, even when the sky is overcast....and the day's just 12 hours or so. (you know, it's light and WHAM! it's dark....there's no "dusk" or "dawn" there, the sun just switches from MAX to OFF and then it's pitchdark
![Laughing :lol:](./images/smilies/icon/lol.gif)
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To make true tropical plants do well in such a tank, you need to add 2 watts or even more for every square decimeter tankfloor (10 cm x 10 cm).
If you have really fast growing plants, you might think about getting one of those CO2-fertilizer equipments.
Fifth; if you have a new plant, or need to remove one that is rooted well, a compost-substrate can "explode" and your tank is a goner; a black, stinking, muddy, gooy mess wich contains invisible fish; and you can strip the entire tank and start again: NOT a nice thing to do.
My planted tanks do well beyond "just OK" with the recipe described, and I stopped using compost (actually I used pottery substrate for indoor plants, less nutrients, but still WAY too much and just as messy, wich I found out, when trying to catch a Mastacembelus from such a tank.....) in 1978....................
My riverine catfishtank:
![Image](http://im1.shutterfly.com/procserv/47b3da31b3127cce96700831ff950000001610)
detail:
This tank contains:
4 18 year old Mochokiella paynee
7 Corydoras robinae
3 Amphilius rheophilus
1 caecomastacembelus cryptacanthus
2 Acanthopsis choirorhynchus (Horsehead Loach)
2 Betta cf pugnax
4 Betta picta