when I re-add salt.I use a 5 gal pail that I throw a tbl sp of salt in and let the water fill it and disolve the salt.its easier to keep track of how much salt you put back in the tank that way.and of course put in your water dechlorinator etc.
i wouldnt use marine salt-use the paper carton API Aquarium salt.You only need to add it once and then after water changes.The goldfish will most likely die -some will anyway and thats good anyway.Just toss em right away so your nitrates dont spike.In my opinion,with death comes life.It causes bb to grow in the tank etc.good luck
