I went in last night to buy some salt (for my 10gl) and you have to walk by the tanks they looked empty,hard to tell with the caked on green and slime alge on the glass so one of the workers started to clean the glass i think just because i stoped to look in and questioned the alge (light brown stringy with bubbles).Their answer it's fine, but the way he was cleaning the glass with a paper towel so i reached over grabed a scrub brush off the rack and told him this might work a little better.When he cleaned out one of the tanks i saw 3 2-3 inch derasa clams,but i had to walk away they make it easy to fight off temptation.