3 questions need help with

[flachef2]

Hi all,
first question is my sandsifting starfish hardly ever comes above the sand surface and when he does my two peppermint shrimp are all over him. I dont know if there cleaning him or trying to eat him, I mean there like a dog to a bone, a moth to a light, on top of him poking and prodding him. The star stays there for a few minutes then disappers. Is that normal?
Question 2- A friend of mine has a salt tank that he is taking down, he has offered to give me his Live rock but he says its been established for about 8 years and he thinks that after a period of time the live rock turns too or maybe gives off silica of some sort that might be harmful to my tank? He was not quite sure if the live rock was safe after a long period of time, does anyone know or ever heard of this?
3rd question - Watchman goby i put in the salt tank (150gallons tall) will hardly ever come out from under the live rock that I have in there. Are they naturally shy fish? He's been in there for about 3 weeks, thought he'd be used to the tank by now. Other inhabitants include two peppermint shrimp, 7 small assorted damsels, sand star, and handful of snails and hermits.
Acutally one more question- I started out with 10 turbo snails and 10 hermit crabs about 3 weeks ago, and Iam down to about 4 snails and 6 crabs. Do you think there is a water problem or lack of food? Are they generally very sensitive to water conditions?
Thanks I appreciate any and all answers
Chef

 

[fbm]

1) I generally read the sand sifting stars are a bad idea. You hardly ever see them and they eat all the beneficial stuff in your sand leaving you with a dead sand bed and eventually a dead star. Peppermin shrimp are probably attacking him, maybe he is sick/dying dunno. Maybe they are camel back shrimp and not peppermints. If they have a hump on there back they are camel back's and they can and will kill things.
2) The older better aged live rock the better IMO. I would grab it without hesitation. Little chance it will leak silicates and if it isn't now it never will. They only way I wouldn't take it is if he ever used copper in the tank that it was in. Copper will leech into the rock and therefore leak out over time, but if he has inverts in his tank and they are surviving this isn't a issue.
3) I don't have a watchman goby, but the behavior you are describing is exactly what I believe he should be doing. I believe they form a cave and just set there and watch. I believe they will form a relationship with a pistol shrimp and then they both hang out in the cave. I have never been interested in them so I don't know for sure.
4) I would say the loss of you snails/crabs was a acclimation issue and not a water problem just because you still have most left. How did you acclimate them. Also if your SG is too low this could cause a slow die off as well. I keep my SG at 1.026 temperature corrected.

 

[saltn00b]

i agree with the above, also the hermits will kill the snails for no reason.
your friend is worried about the LR but for the wrong reason. old tanks used to succumb to 'old tank' syndrome. this is the moment when a tank's calcerous material has absorbed all of the phosphates it can hold, and then phosphates build up in a tank. nowadays, people run phosBan and have refugiums , so you dont see this as much. so it is very likely that this rock had absorbed its quotient of phosphates, so it will not do anything for you in that department, however, it should not leach any back, if it does, it will be minimal and your sand and other rock would just suck it up. take the rock, it is very aged and will be only beneficial for your system.