How deep can I go?

[phoenix]

Hi,
I want to create some height at the back of my aquascape and wanted to know how deep can I go with the substrate before it starts to have negative effects, if any. Are there better substrates to use when you want to get a good depth?
Thanks in advance.

 

[mlgt]

How deep are you thinking? I have a 71cm deep tank and I have my substrate from the back about 20cm or so and the front being about 2-3cm.

I made sure I used a chopstick and made criss cross patterns during the maturing of the tank and threw in about 50 MTS.