Good Plant Substrate?

[xJake]

As we head into the late fall/winter months my local hardware store/garden center is selling crushed volcanic rock (1/8" to 1/4") at heavily discounted prices (less than $1 for a 40lb bag). From what I've read it is a neutral rock that can be used in aquariums. I was wondering if it would have any advantages as a plant substrate as it is rather porous (allowing betting root growth I would imagine) compared to standard gravel and/or if it can be used at all as a plant substrate.

 

[voo]

Check that the rocks aren't sharp as they could damage the fish.

wouldnt the rock be full of all kinds of minerals?

 

[Dubby]

Definitely advantageous as it should have high CEC (ability to store nutrients). Just check that it does not float in water.

 

[xJake]

I bought a bag today to play around with and it doesn't float. It's got some dust on it that I couldn't get separated from the rest of the rock but it seemed to settle to the bottom in just a few minutes (sort of like other plant substrates). As for the fish hurting themselves, I've got some large chunks of it in my 125g and they have yet to hurt themselves on it. Plus, I was just going to use it where I'm putting the plants (back and sides) and I'm putting standard aquarium gravel in the center as an open swimming area.

 

[Dubby]

If you are worried about sharp edges, I would cover it with a layer of sand or gravel. This way, the plant roots can get to them while the fish are not directly exposed to it.