Getting sand underneath gravel

[Lamie]

I am thinking of putting a layer of sand underneath the gravel on bottom of tank. How do you do this with an already established tank?

 

[Lamie]

This is the gravel substrate. Thanks

 

[jaylach]

First question I would have is if you are using under gravel filtration. If so never use sand as it will just sift through the filter plates.

As to doing what you are thinking you would just move the existing substrate out of the way and add the sand moving the existing substrate back over the sand. You would do this in sections.

I DO wonder why you would want to put sand under a gravel substrate. Is this for plants to root? If so most common plants will do fine in gravel as long as those with a rhizome do not have the rhizome buried.

 

[Lamie]

I'll put sand for the plants to put down roots. Then maybe just adding a bit more gravel will also work?

 

[jaylach]

I'll put sand for the plants to put down roots. Then maybe just adding a bit more gravel will also work?

It depends on the plants. Could you give a list of your plants so members with more knowledge than myself can give better advice? For myself all I can say is that all my plants are doing fine in just gravel and/or mounted on deco.

 

[Lamie]

Hygrophila polysperma and hygrophila willow leaf and some crypts. That's what I would like to try

 

[Byron]

Hygrophila polysperma and hygrophila willow leaf and some crypts. That's what I would like to try

The hygrophylla will be no better with sand. These are stem plants and leaves and roots emerge from the nodes along the stem. The cut end of the stems in the substrate will develop roots to anchor the plant whatever the substrate, though the pea gravel (which is what is pictured in the photo) is the largest-size grain of gravel you want. Bacteria is also an issue with large-grain gravel, more than with sand or very fine gravel.

The crypts might benefit from sand. I have never tried to grow them in pea gravel. Mine grew equally well in the finest aquarium gravel I could get, and later in even finer sand. I did have a lot more runners with daughter plants after changing to sand, whether that was cause and effect I don't know.

But of much more significance are the fish species in this tank. Some fish are greatly impacted by the type of substrate. I can see tetras (Hyphessobrycon megalopterus, and I think a "rosy" tetra (?), and these won't care much, but substrate-level fish like cories, loaches, dwarf cichlids do care, and these need sand.

If you have both gravel and sand, the sand will slowly shift to the bottom, being finer grained, though it may take a while. I am also not sure what this might look like. A uniform substrate does create the visual impression of more space, which is for most of us a benefit. Mixing substrates tends not to really "work" and is very unnatural in smallish tanks.