Keeping Substrates Apart?

[Beemeeup]

I have put down a layer of Tetra Plant Substrate for a 175 litre tank which i had from mail order.
i needed some more before i put sand on top
the local LFSs said i needed a sort of cotton wool membrane to maintain separation between the laterite and the sand?
I must have this in order to stop the sand sinking into the tera laterite and vice versa - leaving the laterite come to the surface.

has anybody any experience or advice on uising these membranes - i hope to add water tomorrow to start cycling - help please.

 

[Dubby]

You could use netting thats used for cross stitch. These have large openings which would allow roots to penetrate and at the same time not allow too much intermixing of the two layers.

I have clay and sand substrates and I dont use any membrane. If you put a sufficiently thick layer of sand (over 1 inch) on top of the tetra substrate and you dont have fish/snails that burrow, you should be OK.

 

[voo]

If you have sand that deep you're likely to get anaerobic gas pockets which can be dangerous.

 

[Beemeeup]

thanks for all your help. ive now decided to have 2 cm of tetra laterite and 2 to 3 inches of 1/8th pea gravel - i'm happy with this solution