Who Gives A Fish Forums

I'm stumped. I've had my 55 gallon saltwater tank at the school for years and never had a mass die-off like this. On Saturday, I did my usual 8 gallon water change - nothing out of the ordinary. Monday, everything was fine. Then Tuesday morning, disaster struck. The fish were dead, my scooter blenny was on its last breath, jumping out of the tank with a red belly. I immediately took a water sample and did a 30 gallon water change with distilled water. That's when I noticed this weird white pasty residue on the overflow box and tube - it looked like seagull poop, but no ammonia smell. Water test results were normal: no ammonia, low nitrates, normal specific gravity, temperature, and pH 7.8.

By Wednesday, my flounder and rosebud sea urchin were gone too. I threw in a chemipure bag and used aqua + to remove nitrates and chlorine. Ran another water test: dKH was 9, calcium 380ppm, and no phosphates. This tank's in a faculty lounge, so students do come by, but I haven't had a fish die in two months. That was a copperband butterfly that wouldn't eat. No cyanobacteria in sight, and I'd just done a water change. What's going on? Any ideas on what could be killing my fish? Is there something else I can use to remove any leftover toxins? I still have an ocellaris alive, and I'm hoping my Kenyan Tree Coflake, brown polyps, and mushrooms make it.

I'm curious, why are you using distilled water for your water changes? I came across this article from The Tropical Tank that discusses the potential drawbacks of using distilled water in aquariums.

Torvik22 wrote: ↑Sun Jul 10, 2022 4:53 am I'm curious, why are you using distilled water for your water changes? I came across this article from The Tropical Tank that discusses the potential drawbacks of using distilled water in aquariums.

I work in a lab, so I've got access to a distiller - I just find it easier to use that over tap water, or even RO water for that matter.

I was wondering, do you test the distilled water before mixing it with the tank water to ensure it's safe? I've had a bad experience with store-bought distilled water in the past, so I'm always cautious about the source. If multiple people have access to the distillation equipment, it might be worth double-checking.

Given the severity of the tank crash, I would have expected to see signs of distress earlier if the water was the culprit. However, everything seemed fine on Monday, which makes me think something else might have gone wrong between then and Tuesday.

I've heard some disturbing stories about tanks being kept in public areas, and I'm worried that might be a factor here. Even if it's not intentional, a careless mistake by someone with access to the tank could have disastrous consequences. If the tank isn't already secured, it might be a good idea to take steps to prevent unauthorized access.

I'm inclined to agree with onyzza's theory that someone might have tampered with your tank, either intentionally or by accident. You mentioned the fish were dead, but how many exactly? Did all the coflakes die, or did some survive? It's also crucial to know if there are any cleaning sprays or chemicals nearby that someone could have added to the tank. Given the tank's volume, it would take a significant amount of soap to cause a complete crash, and you'd likely see suds. If someone did indeed tamper with the tank, it's possible they used a chemical that's not typically kept on hand. I hope no one would intentionally harm your tank, but unfortunately, it's not entirely surprising. I also hope you don't consider taking the tank down for good, even if you do find out who was responsible. Marine aquariums can have a profoundly positive impact on children, and I've seen it firsthand.

dreamon7 wrote: ↑Sun Jul 10, 2022 11:19 am I'm inclined to agree with onyzza's theory that someone might have tampered with your tank, either intentionally or by accident. You mentioned the fish were dead, but how many exactly? Did all the coflakes die, or did some survive? It's also crucial to know if there are any cleaning sprays or chemicals nearby that someone could have added to the tank. Given the tank's volume, it would take a significant amount of soap to cause a complete crash, and you'd likely see suds. If someone did indeed tamper with the tank, it's possible they used a chemical that's not typically kept on hand. I hope no one would intentionally harm your tank, but unfortunately, it's not entirely surprising. I also hope you don't consider taking the tank down for good, even if you do find out who was responsible. Marine aquariums can have a profoundly positive impact on children, and I've seen it firsthand.

Thank you for your encouragement. We do have janitors, but they hardly ever clean the offices and they know not to touch the tank. I don't know, other than suds, how I could tell if someone put soap in the tank - I'm just not aware of any other signs. The ammonia levels were 0, so I don't think it was window cleaner. I lost seven fish, which is just devastating - a peacock flounder, six lined wrasse, pseudochromis, two chromis, a blue tang, and a scooter blenny. I think the coflakes will make it, but I haven't seen any hermit crabs moving around and I lost my sea urchin. I am really discouraged. A lot of people took pleasure in the tank. To know that it could all unravel in 12 hours is really disappointing. Whether it was by accident or malicious, it is still very depressing.

onyzza said:

Do you check the distilled water prior to mixing it to make sure it's alright? The only reason I bring that up is I ran into some untrustworthy water being sold as distilled at a store once. If you're not te only one using the distillation equipment, that would warrent checking. However, if there was some toxin in the water that could nuke a tank that badly, I would have expected signs of disress sooner than you saw it. Although others may have more insight, everything being fine on Monday would suggest, to me anyway, that something else went wrong and the tank was nuked between Monday and Tuesday.

Unfortunately I have heard some horror stories over time of what happens when tanks of animals are kept in areas that young and/or irresponsible people, and even just regular cleaning staff have access to it. Cases of deliberately caused tank nukings aside, sometimes all it takes is one accidental soapy hand or a misused disinfectant spray to caues disaster. If the tank isn't set up in some way that prevents other people from having access, it might be worth locking down.

Thank you for your response. It could've been the distilled water, but I didn't buy it nor did I test it before I mixed it - we have a distiller in the lab, because we have to have distilled water for experiments. I could lock the tank in one of our classrooms, but that would be unfortunate, because the whole reason for the tank was for others to enjoy.

That's a crazy story about the glue, I can imagine how devastating it must've been for your family's tank.

Sorry to hear about your loss, FinleyK. I've been reading through the thread and I noticed one question that hasn't been fully answered yet - what's the status of the coflakes? Did they all survive, or were there some losses?

Also, regarding the Saturday water change, was the batch of salt used previously or was it a fresh batch?