Soil As A Substrate

[Adelphie]

Hey guys,

I have finally managed to upgrade my old 80l tank to a 180l tank, and am going through the stage of planning and design.

Previously I started looking at plants after the tank was established, and had a few issues because of it therefore I am keen to get this right from the outset.

Money is really tight at the moment, so I am considering using soil as a substrate capped with pea gravel. I know this can be done to good effect, however I was hoping that somebody with some experience might be able to give me some do's and don'ts. My question is, will my plants get sufficient nutrients from this (assuming that the lighting/co2 are good enough).

I have access to an array of chemicals/trace metals as my mrs is a chemistry lecturer, so are there any additional things that I should consider adding to the soil?

Also if you think that this is a stupid idea, please feel free to say!

Thanks in advance,
Adel

 

[Mr Bliss]

An advantage of organic soils is that there's plenty of matter that's still in the process of decomposition. This generates additional CO2 in the soil which can be utilized by some plants. I'm under the impression that regular potting soil is very nutrient rich for an aquatic substrate though, and may burp up plenty of ammonia and H2S while it gets used to being submerged. But then, a lot of people have used it as their main substrate succesfully so I dunno. I'd definitely boil it first to oxidize as much of the existing ammonia as possible. Mixing it with cat litter would maintain a high cation exchange capacity and help keep the nutrients in the substrate (cat litter adsorbs ammonia efficiently).

Cactus soil is a safe choice, as it's a basically a low-nutrient mix of peat, clay and sand and has a good cation exchange capacity. You can mix in 10 - 20% regular potting soil to provide initial nutrients. That's what I use, capped with sand. Vallisneria and Echinodorus species in particular seem to love this substrate, and I've never had any water quality issues apart from initial cloudiness. Root tabs around the biggest/densest plants may be in order after some months though.

You could also skip the soil altogether, and use a mix of cat litter and sand instead, and rely on some solid fert to add nutrients to the bottom layer. This is what I plan to do with my next tank.

Relying on substrate for fertilization works great with some plants (swords, crypts, vallis etc), not always so well with others. My tank suffered some neglect last summer, there was no water column fertilization for a while, and most of my stem plants started doing rather badly (Limnophila aromatica died off almost completely) while swords and vallisneria just grew into a total jungle.

Cap the substrate carefully and make sure to avoid any fish that like to dig even a little. Be very careful when planting or uprooting plants. There are very fine particles in soil, and the resultant cloudiness can last a long time.

Do plant some of the strong-rooted rosette plants mentioned above. These plants aereate the soil and keep it healthy, as there is a lot of organic carbon in soils, which leads to bacteria prospering in it, and in an anoxic substrate you can get pretty massive H2S buildup.

 

[Adelphie]

An advantage of organic soils is that there's plenty of matter that's still in the process of decomposition. This generates additional CO2 in the soil which can be utilized by some plants. I'm under the impression that regular potting soil is very nutrient rich for an aquatic substrate though, and may burp up plenty of ammonia and H2S while it gets used to being submerged. But then, a lot of people have used it as their main substrate succesfully so I dunno. I'd definitely boil it first to oxidize as much of the existing ammonia as possible. Mixing it with cat litter would maintain a high cation exchange capacity and help keep the nutrients in the substrate (cat litter adsorbs ammonia efficiently).

Cactus soil is a safe choice, as it's a basically a low-nutrient mix of peat, clay and sand and has a good cation exchange capacity. You can mix in 10 - 20% regular potting soil to provide initial nutrients. That's what I use, capped with sand. Vallisneria and Echinodorus species in particular seem to love this substrate, and I've never had any water quality issues apart from initial cloudiness. Root tabs around the biggest/densest plants may be in order after some months though.

You could also skip the soil altogether, and use a mix of cat litter and sand instead, and rely on some solid fert to add nutrients to the bottom layer. This is what I plan to do with my next tank.

Relying on substrate for fertilization works great with some plants (swords, crypts, vallis etc), not always so well with others. My tank suffered some neglect last summer, there was no water column fertilization for a while, and most of my stem plants started doing rather badly (Limnophila aromatica died off almost completely) while swords and vallisneria just grew into a total jungle.

Cap the substrate carefully and make sure to avoid any fish that like to dig even a little. Be very careful when planting or uprooting plants. There are very fine particles in soil, and the resultant cloudiness can last a long time.

Do plant some of the strong-rooted rosette plants mentioned above. These plants aereate the soil and keep it healthy, as there is a lot of organic carbon in soils, which leads to bacteria prospering in it, and in an anoxic substrate you can get pretty massive H2S buildup.

Thanks very much for your post, this is extremely useful.

I have a bristlenosed plec at the moment, who I am worried may stir up the soil, so I am tempted to use a layer of sand and a layer of pea gravel to reduce the risk of the soil being clouded.

Adel

 

[Mr Bliss]

I have a female bristlenose, and there was a time when she decided to dig a cave under a piece of bogwood, clouding the water for a couple of weeks. She's left the substrate alone for a few months now, though. I think males may dig more though.