I’m hoping someone will be able to tell me if Lechuza-Pon is suitable to use as a substrate. This is a product that is supplied for planting houseplants, some of the ingredients sound similar to other things I have seen mentioned on this site and I wondered if it would work in an aquarium.

We use Lechuza plant pots at work, but not the substrate that comes included with the pots so I have got an ample supply. I am about to set up a 260 litre tank and want to use a low light method with no CO2. My plan is grow foreground plants emersed until they form a good carpet, then fill the tank and add all the other plants. This substrate has a size and texture similar to cat litter and looks to be ideal for my purposes, but I’m worried about the fertilisers that are in it. If I cover it with a layer of sand, will it work or should I just forget it and buy a proper Aquarium mix instead?

The details of the mix are as follows: (Taken from the Lechuza website)

Ideal alternative to conventional potting soil. LECHUZA-PON stores added nutrients which are then released to the plants as they need them. It can also retain up to 40% of its volume in water while at the same time maintaining the optimum air pore volume. LECHUZA-PON supports aeration of the roots whilst providing optimum dosage of water to the plants.

LECHUZA-PON plant substrate is made up of pumice, zeolites, lava and fertilizer. The following fertilizer declaration is applicable to the fertilizer: 1 liter LECHUZA-PON contains 3g slow-release fertilizer 15-9-9+3. NPK fertilizer, coated, contains magnesium and trace nutrients effective for 6-12 months. At the end of this period fertilize the plants as usual using commercial liquid fertilizer in the water.

Any advice will be much appreciated. Thanks.

The fact that the substrate is fortified with nutrients makes it a bad choice for the kind of tank that you are planning.

Why not get a bag of the cheapest unfortified top soil that you can find, soak it for a few days (or spread it out in the sun on a sheet for a day), and put it in your tank, cappped with 2mm - 3mm gravel. That will grow plants as well as anything else and you will avoid some headaches and save a few dollars.

Bill

LECHUZA-PON is obviously intended for terrestrial plants, so the Nitrogen in it most likely is in the form of urea or an ammonium compound, such as ammonium sulfate. That can cause big algae problems in an aquarium if any of it gets out of the substrate into the water. Other than that it looks like it might work for an aquarium, as a layer under an inert substrate.

Whatever is in the soil will eventually leak into the water column unless the soil is capped with an impermeable substance, and that would never do in a planted tank.

I once set up a 10 gallon tank with Miracle Gro enriched potting soil capped with an inch of inert gravel. Every kind of algae grew in that tank, and grew very well too. The plants did well also but I didn't see them very often. I took the tank down after 3 months.

Bill

I can't disagree. When I tried Leonardite (Diamond Black) I got yellow water constantly, and it was down under about 2 inches of Flourite Black sand.

Having read your replies I think the best thing for me is to get a decent substrate specifically designed for aquariums, rather than risk a load of problems. Shame though as i have bags of this stuff lying about.

Many thanks for all the advice it has been very useful and probably saved me from making a big mistake.