Unfortunately clam vongole or linguini with clams is about my favorite meal so it doesn't last long in my house. You can keep live clams in your fridge for almost a week and they will stay live. If some die, freeze them. I have put them in my tank many times and they will not live more than a few days or maybe a week. The water is too warm and unless your tank looks like a sewer, they will starve. Here where I collect them I also SCUBA dive and the viability is about a foot or a foot and a half. That is due to the life we have in the water here which the clams depend on. They won't live in a tropical tank.