Gravel in a saltwater tank "no problem"

[ykp53]

at least that is what the lfs told me 3 years ago, and on a yearly basis the PH to my tank drops all of a sudden. I end up putting the fish in a QT and drain the tank and start over. i now think that this problem is because i am using fresh water colored gravel in my tank, so i need to remove the gravel and add live sand. {edit - link} sells sand for 1/2 the price as saltwaterfish.com but it doesnt say "live" what do i need and how deep should the bed be in a fish only 75 gallon tank? and will my tank have to re-cycle?

 

[ophiura]

Couple of things -
What was the alkalinity and calcium in the tank when the pH dropped?
Freshwater gravel provides no buffering capacity so that would be an issue. It also, due to its size, collects lots of debris under it and would have to be vacuumed regularly for sure or the accumulation of organic material would result in pH issues.
And colors painted on might be a problem in some way - but probably not directly with pH.
You don't necessarily need live sand to switch out to. As for the depth, there is some research that needs to be done on that (look up deep sand bed - DSB and SSB or shallow sand bed).
Sorry, I had to edit the name. We do ask that out of respect to the owner and operator of this board, that you not discuss other stores, thanks