jlm9679

Hi everyone, I'm new in the forum, and thinking of setting up a low-tech tank. But before jumping in the El Natural wagon, and after reading all the related discussions in this extremely useful apc forum, I have two major doubts about this system:

1 - Given that a biological filter (ie bacteria) isn't necessary and can even be counterproductive since it 'steals' nutrients from the plants, but considering that the filter would need to be running anyway to provide some water flow - preferably with some filtering material in it to retain the thicker particles - wouldn't bacteria become a problem when they eventually grow in the filter material over time, as they probably will? Would it be a case of getting rid of them on a regular basis, cleaning the filter thoroughly etc?

2 - The potting compound recommended as substrate will eventually exhaust itself in 6-12 months. Would it need replacing with fresh potting compound, or perhaps the thing to do then would be to add fertilizers to the water column instead? Would the fish produce be enough to sustain the plants, once the substrate is finished?

3 - This may be a far-fetched idea, but could crushed egg shells be used instead of the oyster shells that are sometimes recommended for mixing with the substrate?

Any ideas will be very welcome indeed, thanks.

Diana K

1. Nitrifying bacteria and plants do compete for nitrogen, but do not worry about it. The plants will grab all they can, and the bacteria will remove whatever ammonia is left, and the plants will then use nitrogen as nitrates. You WANT these bacteria to live, it is part of the balance you are setting up in your tank.

2. Yup! So you can add tablet fertilizers to the soil, or water column ferts. A soil with a high CEC is good with either. The fertilizers from any source will get in there, just like a checking account for the plants. It will hold the fertilizer available until the plants need it. Fish food may not provide all that is needed, in enough quantity, unless you overfeed your fish so much they can get sick. This is one of the benefits of using a natural soil instead of potting mix. A good soil will have a lot higher level of many fertilizers, and the supply will last longer.

3. Sure can. I would rinse well so no egg remains, just the shell. Break it up really fine for faster effects, but it will all disintegrate sooner, break it up coarser for lighter effects over a longer time. Oystershell grit sold for caged birds and coral sand are the two sources I have used.

jlm9679

Thanks for that, Diana. When you say 'natural soil' vs 'potting mix' you loose me there - I thought potting mix with no added ferts (John Innes, perhaps) was the best and easiest option unless you know exactly what you are doing...

Regarding the oyster/egg shells, what is their function within the substrate? - I have seen it recommeded, but no reason given for it!

Also, another point I forgot to include in my original posting: would you recommend using clean fine sand (beach sand, basically) instead of the usual fine gravel for the top layer, would it have any disadvantages that you know of?

wkndracer

Sand would work its way through your soil or mix with it (IMO). In too deep a layer it can also interfere with the gas exchange. What too deep would be I couldn’t say. Ms. Diana is the wizard on this stuff. When I started planning my tank pool sand was my intended capping material but after reading posts I switched.
The bacteria and filtering question I’d also like to post an option on. Reading the book and website information the primary purpose is to provide circulation in the tank. What I use is a power head connected to a DIY spray bar equipped with a Marineland reverse flow sponge kit. This moves the water well and removes any large partials while leaving everything for the plants. It’s very easily serviced and is working quit well so far. Other than the power head I used an air driven sponge to help the tank over the hump as the soil cycled converting to a submerged state.
Hope you jump in and start a tank! Best of luck!

dwalstad

For tanks with extremely softwater (GH <4 and < 70 ppm CaCO3), I suggested that hobbyists add a little calcium to their substrates or to the water. If your water has a normal water hardness, then you probably don't need the additions.

This information is in my book (pp. 86, 137, and 185).

jlm9679

Yes I have heard that sand has several disadvantages, so I think I'll stick to fine gravel instead, thanks for the advice!

jlm9679

I suspect that the tap water in my area (London UK) is fairly hard, so there should be no need for added calcium. Thanks, Diana

Diana K

By natural soil I am saying garden soil, but it needs to come from a location without any pesticides, or any other pollution.
Some soils work really well in tanks, some do not.