Cloudy water, tank crashed, please help


New member
Hello everyone,
Although I am a member and have learned a lot on this forum, this is probably my first thread, and I have sad news and need help and advice.
My eleven year old mature marine FOWLR with some softies tank, crashed 3 weeks ago and I urge you to read the story first and then advise.
I am a dentist and this tank is in my reception area, but only access to tank is from a back room, aka our consult room, from where our aquarium maintenance guy cleans display tank (DT) as well as the sump below it. We feed the tank every day from this side as well.
On the night of March 6th 2019, early morning of March 7th 2019, our immediate neighboring falafel restaurant mysteriously caught fire, and although the fire was mostly contained in that unit, the smoke spread to all adjacent units including ours. When we were summoned by our alarm monitoring company at 0115 hours, the fire had probably burned for some time and acrid smoke was spilling out of all adjacent businesses including our clinic. Needless to say, once the fire was contained in the restaurant and put out and smoke was exhausted from everywhere, we still were closed for about 2 weeks as insurance dispatched cleanup crews to deal with smoke and soot accumulation. The restaurant fire went into an investigation and for the first two weeks, our cleanup process focussed on getting the smoke smell out of everything in the clinic.

Luckily, the fish and inverts seemed to be not affected by any of this initially.

The restoration company then used a organic shellac based smoke sealing primer spray in the ceiling space of the clinic to lock the lingering smoke smells. This Zinsser BIN shellac base smoke and stain blocking primer has high Volatile Organic Compounds (VOCs) and the crew worked with special respirators. Now EVERYTHING below our ceiling tiles was covered with plastic sheets, and the aquarium and sump are enclosed in cabinets and were covered with plastic sheets to protect the aquarium, small 4"x6" grates in cabinet doors were left open for air, but had a sheet draped loosely on it. The system ran on its schedule and everything seemed ok. The next afternoon, water started going cloudy and all fish died, including anemones, mushroom corals, all inverts, even the blind Nassurius snails came out of the sandbed and were dead. The stink of dying fish was immediate and the sump was covered in white, frothy foam. The saddest day of my aquarist life was to use nets and dispose of 6" majestic angel, 7" regal blue, 10" sailfin tang and about 14 total fish and many more inverts including shrimp, starfish, anemones, elegance corals, etc.
The protein skimmer had gone into overdrive. The skimmate cup had the dark gunk but this time the frothy foam had pushed out of the cabinetry and the plastic wraps that were covering the aquarium cabinets. Stinky foam covered everything.
I immediately turned off the skimmer, removed as many dead fish I could see through the cloudy water and called for help. My maintenance man came in 2 days later and did a 70% water change. Did it twice in a week.
The smell abated but did not go away. A few days later, the restaurant next door, which was completely demolished inside all the way to the condeblocks wall, was spray painted with the same smoke sealer from inside, Zinsser BIN primer, smoke and stain blocker. We saw the soot covered black space turned white in 2 days, and their lingering smoke smells dropped dramatically too. We could smell an oil paint smell for a couple days.
But my tank went cloudy again!
Empty tank with zero livestock with just live rock and sand bed went completely cloudy! The stink came back! What is left in an empty tank to die ? I guess the 10 years of accumulated nitrifying bacteria died?
I don't know what to make of it.
I ordered ALL live rock and ALL sand in DT and SUMP be removed and disposed. Even the caulerpa and chaeto in the sump was thrown away.
Both DT and Sump were left emplty and bare for a week. The stink finally went away. I decided to start the tank afresh. FOWLR to begin with for first few months, I planned to use the live wet sand sold online in 20 lb bags to jumpstart the cycling.
Just to rinse the system again, I filled entire system with cold tap water and let the Laguna pump cycle the water from DT to sump and back to DT, with only the white filter media to catch any dried and peeling coralline algae now seen in occasional flakes on the overflow column. No lights , no skimmer.
2 days later, this water has gone cloudy again and smell of dying fish is back!
I have no more ideas left and am constantly trying to assess and remedy, but I have to diagnose this problem first. Our clinic is limping back to normalcy but it's just not the same without our beloved marine aquarium to keep everyone entertained and calm frayed nerves. This time I am at my wits' end, and need advice.
Tons of photos in my phone but could not upload any and there is some severe restriction on file size?
Please help.


New member
I'm sorry you went through that. When I first read it, I was thinking, "that's odd, shellac is non-toxic, and the ethanol it's dissolved in isn't either". But it does appear that at least some formulations of Zinnser's B-I-N primer contains a substantial amount of acetone, but I believe it's the spray cans.

Here's what I think happened, but this is pure speculation. I'm guessing that your tank got a huge dose of ethanol from the spray equipment, so it was similar to overdosing a tank with vodka. Most that do carbon dosing know that a little is OK, but a lot will cause a massive bacterial bloom, a subsequent oxygen crash, and everything in the tank gets nuked.

That's one possibility, yet another is that the restoration company added an anti-mildew and/or anti-bacterial agent to the materials that they were spraying. One of those could've been benzalkonium bromide (the stuff that's in Lysol). If so, it's deadly toxic to marine life in ppm concentrations.

At any rate, since your tank was running so long, It's a pretty good bet that the inside of your plumbing was coated with marine life. When you replaced the water with tap, it's likely that whatever remained on the inside of the piping died, and it took a day or two for the inevitable bacterial bloom to develop that was feeding off of the dead critters in the piping. The correlation with more of the spray may have been a coincidence.

In any event, since you've emptied everything out of the tank, your best course of action is to bleach it. I'm guessing that it was at least 200 gallons with the fish that you describe, so I'd suggest 2 whole gallon bottles of plain bleach. Note - do not use bleach with "chloromax" in it - this is a detergent and polymer mixture, and you don't want that in the tank. Just buy cheap-as-dirt store brand chlorine bleach from the home store.

It will work with the existing water in the tank and sump, but a better course of action would be to drain it and refill it with tap water. Leave this circulating for at least 24 hours, after which you can add sodium thiosulfite to neutralize the bleach, or just drain and rinse the tank.

It's a shame you tossed the rock and sand - it could've been rehabilitated (at least assuming you're going to set the tank back up).


New member
Hello dkeller,
Thanks for your assessment and prompt reply. So a bacterial bloom is what it is. The VOCs from the BIN spraying was harmful enough that the company ordered everyone out for two days, covered everything with plastic and wore respirators themselves, overpowering smell of oil paint prevailed for two days after.
I feel a bit afraid to add bleach to the system, never done it before. Does the bleach kill the bacteria right away? Will the cloudy water turn clear right away?
How long do I run this dilute bleach water system?


New member
Yes, it will kill the bacteria right away. I'd leave it circulating overnight to oxidize the buildup in the pipes. One aspect of this is that it's likely that your clinic will smell of bleach, so you might want to do this on a weekend so that you can let it circulate, then either drain the system or neutralize the bleach so you can air the clinic out before patients arrive.