Okay just a heads up so you don't make the same mistake. I had (notice past tense) flowing around in my sump. More so just to get a temp. reading just cross check with my controller. Well it broke and all of that mercury flowed into my tank. Every thing closed up. When I saw that I did a reading of all my water parameters and got ammonia 0, nitrite 0, SG
1.025, nitrates 0. I said "Oh heck" haha and did a hugh 50% water change since I had the water already made up and all was stable, Temp, ect...
That was yesterday...Today everything looks a good as ever...Be careful if you have one of these.