Odd problem with new tank

Keith Lingenfelter · Feb 16, 2016

I purchased a 55 gallon aquarium several months ago with plans for setting up a reef aquarium and have run into an odd problem. Before setting up the tank I washed it lightly with tap water then filled it, and set the salt level. I filled it with water pre filtered with a whole house sediment and carbon filter. However, I noticed ring of what appeared to be like a bath tub ring around the tank from the bottom up the side about 1/2 way. It was not visible before salt water was put in the tank. It would not come off by simply wiping the tank walls with a cloth. Anyway I let the tank sit for about a two weeks and did not try to clean this ring off. The tank had live rock installed. I finally did clean the ring with a single edge razor, I had to scrape it while the tank was full and got most of it off, but not under the gravel at the bottom. The water tested proper for PH and salt level and very low nitrates, etc. Finally I put several inexpensive fish in the tank to test things out. They all died within a day or two. I tried this again in another week and again they all died. Now I fingered the something was seriously wrong, maybe associated with the ring. It was still there in the back and at the gravel level. So I drained the tank and thoroughly scraped it off all through out the tank and rinsed it with clean water. I also now have installed an RO filter just for the aquarium water. I've now filled it again and no ring. The seller of the tank says that nothing was ever put in the tank while in his store and says it's new. He is reputable I think, I've been buying from him for years, for my other aquarium (marine).
My question; does anyone have any idea what this ring of stuff that was sticking to the tank sides is?

CodyRVA · Feb 16, 2016

Hard to say what the ring could have been, but adding fish only 2 weeks after starting a system tells me the system wasn't cycled, regardless if the rock is live. Could have been the ring, could have been a spike in ammonia, could be both. How long was the tank sitting around before you used it? If you did everything the same the second time, with the exception of the RO filter, and you had no ring, that tells me the ring was caused by something already in the tank. I doubt skipping on the RO filter would create the ring/kill the fish, unless your water is incredibly bad.

Keith Lingenfelter · Feb 16, 2016

Well the water works fine in my other marine aquarium. Ammonia and nitrates were OK just before the addition of the fish, tested by me and the aquarium shop. And the ring had to be in the tank when I purchased it. Just baffling what it could be. It would only come off by scraping it off the glass with a razor blade. Of course when I did the first scraping the tank was already full and whatever it was was then in the water. The second scraping required the tank be drained and then fully cleaned.

CodyRVA · Feb 16, 2016

Gotcha. Clearly something was either in the tank once before, or it collected dust/dirt/grime from sitting around. If you've got it perfectly clean, filled back up, cycled, and you successfully add fish then, sure; whatever the ring was, killed the fish. Were you monitoring the salinity before and after you did the scraping?

Keith Lingenfelter · Feb 16, 2016

Yes before and after. Anyway it will likely remain a mystery. The ring did not show up until salt water was added, so the "new" tank looked OK in the store. I've had aquariums for years and never encountered any thing like this before. I hope never again.

Diesel · Feb 16, 2016

You didn't make any picture by chance?

[HASHTAG]#reefsquad[/HASHTAG]

CodyRVA · Feb 16, 2016

Yea thats a mystery. My guess is the tank either collected something in store or before being used, or it was previously used.

Keith Lingenfelter · Feb 16, 2016

No no pictures, but it looked just like the old bath tub scum ring, but it covered the tank walls from mid way up down to the bottom and there were "splotches" around the top of the glass also. The color was light an to grey. And as I said it was not visible with no water, or I would not have taken the tank home.

human · Feb 16, 2016

Sounds like who ever had the tank before you just let it sit and evaporate, leaving mineral and calcium deposits. Maybe let it soak in vinegar for a few days to help break it down.