Hi Sweatpea... You grabbed an old post from last year, but it was a real good lesson to learn when it happened to us! That situation really frustrated us. All our tests looked pretty good if I remember correctly, and the blah! We couldn't believe how things had changed in our tank. All that money you put into a new hobby, and then a water change suddenly threatens to wipe out your new aquatic world. There is a big difference, and we'll never do a switch like that on our critters ever again. We were pretty new to reefing when we designed this board, so we have grown with the site! It's amazing what you pick up from other's help.

You should be ok the way you're doing things, but I would suggest buying from the same place each time, if at all possible. Don't be afraid to ask the store exactly what they are using, and if they're consistant. With any luck, the water is likely the same they are using to support their sale tanks. ....Angel

PS. Welcome to the site! We're glad to have you here!