Gordonrichards

Hi, silly question to ask, but here goes.

I have a 33 Gallon long. How much substrate will I need?

I am planning on having a .25 inch layer of mixed worm castings and sand at the bottom of the entire tank. I will have a small slope in the back which will have an additional layer of mixed worm castings and sand. In my mind this will allow me to have plants which root deeper in the back of the tank.

On top of the mixture, could I get away with using two 20 pound bags of eco complete?