Think that I may have a case of ich

So all of the crabs, snails, star and LR would be ok? Will this product kill the parasite?

Yes all will be fine. And yes it will kill the ICH.
 
Also I don't have any kind of sponge so I wouldn't have any kind of biologic filter. Is there anything that I could put in there to help? What about water, do I take it out of the display or would it be all new?
 
Your LR is your bio filter. Leave your water in and add the treatment as directed. If you follow the directions on the bottle you will be fine.
 
If I do pinpoint this as ich, wouldn't all of the fish show signs of it?

That depends on how long the infestation has been in your tank and how many cycles the ich has been through. Each cycle will produce more offspring leaving more parasites to infect more fish.
 
Also I don't have any kind of sponge so I wouldn't have any kind of biologic filter. Is there anything that I could put in there to help? What about water, do I take it out of the display or would it be all new?
Sorry I was meaning if I set up a QT tank.
 
Many people have claimed to have had success using 'Chem Marine Stop Parasites', as well. It too, is reef safe.
A good micron filter and a UV sterilizer will go along way in removing and killing the free-swimming parasites, as well....along with lots of water changes.
 
In a QT situation where you think there is a parasite such as ich, I'd not use old tank water. If you go the QT route that I mentioned earlier you'll probably have to do frequent water changes (every other day or so) but it is possible.
 
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