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My small change on soil substrates
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