I just noticed this yesterday. I know there's a ton of threads about this, but they seem to be about established tanks. Mine is still cycling and the only living thing in it should be whatever came with the Dr Tims One and Only that I dumped in a few weeks ago. The bed is regular (dry) sand and the rock was dry rock from BRS, which I still soaked for a few weeks anyways. The tank has been all put together, with the RODI water, salt, dr tims and some ammonia for 3 or 4 weeks. Nothing else has been added since then.
I noticed this yesterday and at first thought maybe something in the water was causing some of the caulk to dissolve. What was odd was that it seemed to hung up on edges of things (As you can see in the video), but if I tried to pick any of it up it would fall apart in my hands. At one point, when I started messing around with the filter socks, the entire sump was clouded with it, but even then I couldn't actually get any of it out of the water with my hands. The best I could do was to knock it loose as much as possible and let it get caught in the sponge filter between the protein skimmer and return pump. So far, I think that's what's happened as none of it seems to be in the DT.
I know there's not much too look at here, but it was the only picture I could get once I realized I should take a picture.
Also, FWIW, off the top of my head, ammonia is a about 1ppm, Nitrite is at 0, Nitrate is 0-5ish (API tests, so not always easy to tell) and because somewhere along the line someone on some forum mentioned Phosphorus levels.
Short video
My fingers are crossed that this is just part of the cycle, but I really have no idea.
I noticed this yesterday and at first thought maybe something in the water was causing some of the caulk to dissolve. What was odd was that it seemed to hung up on edges of things (As you can see in the video), but if I tried to pick any of it up it would fall apart in my hands. At one point, when I started messing around with the filter socks, the entire sump was clouded with it, but even then I couldn't actually get any of it out of the water with my hands. The best I could do was to knock it loose as much as possible and let it get caught in the sponge filter between the protein skimmer and return pump. So far, I think that's what's happened as none of it seems to be in the DT.
I know there's not much too look at here, but it was the only picture I could get once I realized I should take a picture.
Also, FWIW, off the top of my head, ammonia is a about 1ppm, Nitrite is at 0, Nitrate is 0-5ish (API tests, so not always easy to tell) and because somewhere along the line someone on some forum mentioned Phosphorus levels.
Short video
My fingers are crossed that this is just part of the cycle, but I really have no idea.


