All fish dead after water change - what went wrong?

[UnnamedReef]

Two clownfish and one cardinalfish. I retested my RODI water and got between 0 and 1 ppm. Yes I have a pressure gauge, I run the membranes around 60 psi, it's a 5 stage. Relatively new, with it reading 0-1 I think the RODI unit is ok

 

[Stevorino]

This tank looks ultra new.... It's possible that the water change/scrubbing of rocks had nothing to do with it at all and was just a timing coincidence.

- How long has the tank been cycled?

- How long were the fish in there before dying?

- What and how much were you feeding?

 

[TX_REEF]

Ok, I see, that seems fine. for RODI make sure you flush the RO membrane (flip the black valve switch to open) for 30 seconds or so before and after making water to flush any residue. Can you tell me about your cycle and how that went? What equipment is your tank using? I know "random" fish deaths are extremely frustrating so doing my best to assess your situation

 

[UnnamedReef]

I've had the tank for over 2 months, cycled for about a month before adding fish. Watched my ammonia, nitrite, nitrate rise during the cycle so I was pretty confident it was complete enough to add fish. The fish have been in there about a month with no signs of problems. Feeding frozen mysis shrimp (1/2 cube per day, targeted at the fish with a baster) and occasionally flakes. With no problems before the changes, I think it was something I did

 

[Stevorino]

I've had the tank for over 2 months, cycled for about a month before adding fish. Watched my ammonia, nitrite, nitrate rise during the cycle so I was pretty confident it was complete enough to add fish. The fish have been in there about a month with no signs of problems. Feeding frozen mysis shrimp (1/2 cube per day, targeted at the fish with a baster) and occasionally flakes. With no problems before the changes, I think it was something I did

I'd be interested to hear others' opinions, but my best guess is that the bioload in the tank was suuuuper low because of light feeding, so that when you stirred it all up there was an ammonia spike that killed the fish. Corals can have delayed reactions.

Light feeding and the water changes explains how Nitrates were virtually non-existant. At least for a while, I'd shoot for Nitrate of at least 5ppm, if not 10+ until you get through the ugly stages.

It's also possible the clowns and cardinal were being underfed so it didn't take much to knock'em out.

 

[Rewd]

Who are "local water guys?"

Employees at the local municipal water facility.

 

[TX_REEF]

The only things I can think of are ammonia spike due to stuff getting stirred up rapidly, or a lack of oxygen, possibly due to lack of surface agitation, or perhaps a combination of both.

 

[UnnamedReef]

I've had the tank for over 2 months, cycled for about a month before adding fish. Watched my ammonia, nitrite, nitrate rise during the cycle so I was pretty confident it was complete enough to add fish. The fish have been in there about a month with no signs of problems. Feeding frozen mysis shrimp (1/2 cube per day, targeted at the fish with a baster) and occasionally flakes. With no problems before

 

[UnnamedReef]

Seems an ammonia spike is the leading theory. How does stirring up the sand bed and scrubbing the rocks drive an ammonia spike? Asking so I can avoid that in the future.

Guess I need to feed more when I get more fish, it'll be a few weeks before that happens though

 

[Crustaceon]

Here’s my take: When you have a tank with a light bioload, low nutrients and immature rock and then impart a massive “pollution” event, you’re probably going to have an ammonia spike because even though your tank is cycled, it’s only cycled to keep up with a near pristine tank and barely any waste being produced. IME, dirty and more mature tanks are FAR more resilient to this happening because the beneficial bacteria population is so robust and can better cope with ammonia spikes. In all honesty, you WANT your rocks to initially be covered in algae. You WANT diatoms on your sand in the beginning. I consider that a badge of honor because it’s all part of the process to have a healthy tank in most cases and both conditions are easily remedied in a mature tank.

 

[UnnamedReef]

That makes sense to me, my highest bio load tanks have always been the most resistant too now that you mention it. I was definitely more delicate and conservative with this marine tank since it's my first one.

Where would you recommend I go from here? Start feeding the empty tank (except for my emerald crab) to re-cycle?

 

[Reefer_kano]

What has been the temperature of your new salt water when doing water changes?

 

[Stevorino]

That makes sense to me, my highest bio load tanks have always been the most resistant too now that you mention it. I was definitely more delicate and conservative with this marine tank since it's my first one.

Where would you recommend I go from here? Start feeding the empty tank (except for my emerald crab) to re-cycle?

I would indeed keep feeding the tank. Personally, I'd bump it up to at least a cube a day, but you will undoubtedly get varying opinions on how much.

After a week or so, if Ammonia and Nitrite stay zero and Nitrate is over 5ppm, I'd go snag another pair of clowns.

And FWIW, that rockwork is gonna look like total **** soon. There's no way to avoid it with dry rock like that. In fact it'll look like **** for months! Don't feel the need to scrub it all out every time... major disruptions of the tank set back progress more than you can imagine.

 

[Crustaceon]

That makes sense to me, my highest bio load tanks have always been the most resistant too now that you mention it. I was definitely more delicate and conservative with this marine tank since it's my first one.

Where would you recommend I go from here? Start feeding the empty tank (except for my emerald crab) to re-cycle?

If the tank is already cycled, the best course of action is just to feed the tank to maintain maybe 10ppm nitrates and keep some snails to chew on stuff and produce waste. Watch your rocks for coralline algae. Let everything go through its phases and when your rock has a fair amount of purple on it, then’ I’d start adding fish again. Give it a month or so. It’ll happen when it’s ready and honestly, I wouldn’t care about appearances until I started seeing purple spots.

 

[UnnamedReef]

Thanks everyone, I'll increase my feeding and test every couple days to see where I'm at. I won't be getting any new fish until after the holidays at least, so that should give me plenty of time to make this tank more robust. Appreciate all the help, today was a bad day but nobody ever said this hobby was easy.

 

[blecki]

Scrubbing cyano or diatoms will not kill fish like that. My money is on chlorine in your tap water getting past your RODI somehow. I did that to a freshwater tank a couple years ago after a water change and wiped out an entire tank in less than a half an hour. When I spoke to the local water guys they did tell me that sometimes municipal water agencies will occasionally spike the water supply with a higher level of chlorine on a seasonal basis.

Not enough people realize about CHLORAMINE. Chloramine is not removed effectively by ordinary carbon blocks the way chlorine is. It will tear your membrane up and exhaust your DI very quickly. If it makes it to your top off / water change water it does not gas off. That's why water treatment plants have started using it more and more. I don't think it's directly harmful to fish (anymore than it is to us - we drink tons of it and are fine) but it will kill your biological filter and cause an ammonia spike.

Should I do more water changes in case something got into the tank, or would I be doing more harm than good?

If you suspect bad water then absolutely do not do another one using the same water!

Seems an ammonia spike is the leading theory. How does stirring up the sand bed and scrubbing the rocks drive an ammonia spike? Asking so I can avoid that in the future.

Yes, but, your tank is so young and relatively clean that I really doubt there's enough in the sand to cause any issues.

 

[Malcontent]

Employees at the local municipal water facility.

That's an odd thing for them to say. Maybe they're referring to pre-chlorination but that's an archaic method that, in the US, runs the risk of elevating disinfection by products regulated by the EPA.

Chlorine levels out of the tap do not "spike" and nobody has ever detected such a spike other than aquariumscience.org who likely fabricates most, if not all, of his experiments.

Get a Hach DR/300 at a minimum and measure total chlorine levels every time you run the tap for an extended period. I do it after making RO/DI water. 30+ measurements over 1.5 years and not a single spike.

This myth is so pervasive among freshwater keepers that I made a bingo card:

 

[blecki]

Don't know why they would spike it but they do occasionally switch from chlorine to chloramine and not tell you about it.

 

[DCR]

I don't think it is that unusual for a water treatment plant to occasionally shock the distribution system with high levels of chlorine or chloroamine.

 

[Rewd]

I don't think it is that unusual for a water treatment plant to occasionally shock the distribution system with high levels of chlorine or chloroamine.

I think this is what they were getting at. For the longest time, I thought they didn't put chlorine in our water at all and it was all just pumped from some well. I was half right on that. They did tell me that by the time it gets to my particular place of residence, there is almost no chlorine left and that generally, they only put the DEP minimum amount. We live in an unusual area where we are far enough out that we are on septics, but still manage to have a small municipal water system.