[squawkbert]

In my 5g, I had an "open type" checker go yellow on me, I mounted it outside the tank. It stayed yellow for 3-4 days, then went back to green, still hasn't gone blue.... I thought that maybe some acetic acid residue from the silicone used to assemble it had found its way in. I'm going to keep it in the air & see if it ever goes blue.