i have a standard 20 high that i added 1 25lb bag of eco-complete to. the tank is now cycled as as i start to plant it i think i need a deeper substrate. could i add some regular gravel on top of the eco complete, and do i need to remove the inhabitants to do this? there are curently 2 platies some snails and a shrimp. The tank is going to house a f8 puffer when the lfs gets one in for me and the platies will be moved back to the 45.