Will my tank cycle again if I switch the substrate?

[devinws]

I have 2 inches of gravel in my tank. There is one discus, one pleco, 3 cardinal tetra, 6 neon tetra, and 18 cory cats in the tank. The tank is 75 gallons, 82 degrees, one water change weekly of 40%.

I have five discus on the way from Kenny's Discus. They should be here in about a week. I have read that keeping one half inch of sand is desirable over the large quantity of gravel that I have. I want to remove the gravel and add white pool filter sand. The tank has been running for several months and has cycled. There is a large ornamental driftwood in the tank that also likely has beneficial bacteria.

Will my tank go through a cycle if I switch the substrate out? Really want to do this before the other fish arrive but don't want to submit them to a cycling tank.

The discus are 4.5, 4.75, 5 inch, 5.5 inch, 6 inch, 6 inch. Is my tank overcrowded? How many tetra and cory cat can I go down to? I would remove the pleco as he is about six inches, but he is a golden bristle nose and I have kept him for quite a long time. I believe 6 inches is as large as they get.

Basically just nervous I'm going to kill my fish. Help me out guys.

[brady]

What type of filtration are you using?This will have a bearing on your the ability of the tank to maintain its bacterial load. Removing the substrate should not affect your cycled tank.In fact you when you remove it I would leave it bare bottom.Easier to keep clean and lessen chance of disease. In my opinion 40 % a week is not enough, should be more like 75 to 100% at least twice a week if not more.
Jay