How many pounds of substrate for a 75 gallon?

[dapellegrini]

I used to vacuum out all of my gravel in depth. Haven't done that in years. Only vacuum the surface now. I see no need to clean the gravel at any depth, past sucking the mulm off the top. Maybe something to do with having plants?

 

[hc8719]

I never had a problem doing a complete tank gravel vac before the water level got too low (when I had gravel substrate). You just have to watch how fast you have the siphon. Not difficult at all IME.

depends on your fish waste, i have plecos and gouramis