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My small change on soil substrates

Hello All:

I've been following the "discussion" on the merits or lack thereof of 
the various substrates. Here is my personal experiance.

I'm currently running a soil substrate 50L (about 10 gallon) tank. 
I've got yeast CO2, 3.6 watts per gallon of 6500K Osram Biolux 
daylight tubes with polished aluminium reflectors, no filtration, 
20% water changes every three weeks.

Anyway the substrate is 1cm of local red subsoil, then about3 cm 
of clay topsoil mixed 1/2 and 1/2 with vermiculite, then a layer of 
swimming pool filter sand, also about 3 cm. The tank has been running 
for about four months now. I'm getting growth that even my colleagues 
can't believe (I'm a botanist).

Tank has seventeen species of plant. My Mexican Oakleaf is growning 
right out of the tank, my three species of Ludwigia and my Hygrophila 
would if I didn't prune them every three weeks, my Limnophilia has 
taken over the back of the tank, and I scoop off about 1/2 square 
foot of some Lemnaceae species (its not Lemna, rather a related 
genus) every week. I fertilise with MgSO4 and K2SO4 according to 
Steve's recipe, although I haven't added fertiliser for a month and a 
half now. I stopped adding the KNO3 as it seemed to be causing algea 
problems. The only algea I can see in my tank is some on the side of 
the glass in the soil layer, and a fair bit of thread algea that I 
just remove mechanically. Anyway it doesn't bother me.

Things like laterite just aren't accessable here (they're available 
here, just very expensive. A typical fishtank light cost costs what 
I earn in two days.)

All I can say is that soil substrates work. You need to set up a 
soil tank properly before you can judge whether soil tanks are good 
or not. Sure not all soils are  equal. The local soil I used is 
rather poor. If anything that's why I chose it in the first place, to 
ensure that the substrate wasn't too fertile. The vermiculite was 
originally just me combining Steve and Jim's recipe's, but now I use 
it because of its CEC. I have a suspicion that after the initial 
algae bloom, it captures much of the dissolved nutrient ions and 
keeps it from entering the watercolumn. The Chem department agrees 
with me on this.

Sure my substrate isn't natural. I wouldn't use pond mud if you paid 
me too, especially here in SA. All those Noo-Noo's are a bad idea in 
what is essentially an artificial environment.  All I know is that 
terrestrial soil works, and it works well. Just keep it out of the 
water column.