actually no, its normal aquarium gravel - because this tank started off as a true brackish aquarium (sp gravity 1.005 at first) back in 2004 when I first set it up..I slowly increased the salinity over time. I used to have big archers in there too, but I had a nitrite spike in 2006 after adding medicine for ich to the tank - wiped out my bio filter and they didn't make it..
I do keep shells in the tank to keep the pH up, my hermits seem to do fine.
I have been thinking about switching to aragonite or marine sand, but have held off because I don't get very much algae in this tank at all - probably because the pH is on the lower side of normal saltwater pH and I do NOT use RO water which is pretty standard with saltwater folks too - cuts down on algae growth.
I am afraid if I go with the 'correct' substrate, I will end up battling more algae.
my monos have been doing great for the last 5 years, so I haven't got around to changing over yet..
here is are some shots from last year of the monos that will be going back in tomorrow evening:
