Polyps & Polythoa

The sundial snails I have seen are the size and shape of Astrea snails with a peculiar design on their shell. If the ones you have are not like this then, unless you actually see them eating coral, they should be left alone. 

Yes, coral do grow better with more turbulant flow caused by turning powerheads on and off, but a powerhead that isn't running is worse than having the current always going the same direction. The only powerheads I know of that can handle on-off cycles are Maxijet. That's why I use one modified MJ1200 for the excellent way it can totally change the direction of current in my 75 gal which has two other powerheads at each bottom back corner pointing up toward the surface.
I would definitely remove the timer from those powerheads and look at repositioning them so they create a movement of water from the bottom to the top of the tank. The top of the water should look like this:



You can spend time testing Alk every day if you want, but it probably will take 1-2 weeks to come down to 10.

Yes, the jar sits on the sand leaning against the rock, so the crab cannot crawl back out. The crabs you mention could be the culprits. They may be eating coral because they either cannot get to the snails or they prefer coral right now. When you catch them take a pic and show us so we can tell you for sure.

Imagine this MJ1200 is inside the tank shooting water up to the surface. Two of any brand powerheads at opposite bottom corners of the tank shoot water up diagonally toward the top front surface. One modified MJ1200 on a timer moves water one way for 6 hours and the other way for the next 6 hours. The timer only stays off for a few minutes between cycles. It works and doesn't cost an arm and a leg. I think I have a pic of the modified MJ.


Here is the modified MJ1200



Edited by Mark Peterson - October 17 2008 at 9:58pm