Fish dying suddenly ... could it be Kent Magnesium?

Maga18

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I had flame hawk (RIP), file fish (RIP) and a fire fish (probably also RIP somewhere in the rocks) in a 65 gallon, nothing fancy, but fish was happy and I had a modest mixed reef, going well.

Parameters: alk 8.3 calcium 450, magnesium 1250 (raised to 1300), ammonia (Seneye) (0.017 ppm), temp 78F.

I bought some corals from a fellow reefer from what he described as a "neglected", but otherwise healthy tank (although I did not see the tank regrettably).

I dipped all the corals in coral Rx before putting in the tank yesterday.

Today, since frags included some freebie "sticks" that the guy could not sell I decided to up my reefing game and check what has been going on with magnesium ...

The Red Sea test showed 1250 ppm so I decided to slowly raised it, I added 30 ml Kent Magnesium (which should raise Magnesium ~10 ppm) and other than that use super glue gel (which is generally reef safe) to mount some of the frags.

Other than that I added couple of cups of Instant Ocean saltwater to compensate for water removed from the frags. Seneye was warning me before that instant ocean had relatively high (up to 0.12 ppm) free ammonia levels (I checked that some salts have ammonia).

I just realized recently that this salt has ammonia, I have been running Seneye in my tank and noticed that ammonia has been rising with each water change. But it never went above 0.05 ppm free ammonia and last two days had been going down up to 0.02 free ammonia. I added only couple of cups of this premixed salt water which previously tested borderline high for free ammonia, also when I am testing the remained of the premixed salt water now it shows (so far) no ammonia.

My main suspect is currently Kent Marine, since it is supposed to have some impurities, I have not used it in a while, and in hind sight, I should have shook it more thorough fully :(

I do not have photos, got too bummed to make them.
First fish I just found dead on the bottom, started to look for another and it was swimming funny, convulsed a bit, and died within minutes since I was afraid to but it in the premixed saltwater that I though was worse - and anyway had just couple inches left at the bottom of a large barrel ...

Based on at least one fish dying suddenly I would be guessing it was soothing chemical not a disease. But I confirmed with a test that Magnesium raised at most 50 ppm and I added only 30 ml, even if it was not mixed well should not be huge. I also know that high magnesium levels are ok, had the once above 1600 to fight algae ...

Snails also seem ok, the few that I can see

Corals seem slightly ticked off the moment second fish was dying but now look mostly ok (lights off), but eg sun coral is extending polyps again.

I am preparing Tropic Marine salt that I recently bought and I was thinking 40% water change ...

But I would really like to understand what has just happened?

Should I wait months to add fish again in case it is a disease?

Seneye is supposed to be very accurate and was showing completely safe free ammonia levels when fish was dying - the ammonia even slightly lowered after their death reflecting the do not produce it anymore?

the levels have been approaching Seneye first alert levels (0.05ppm free ammonia) two days ago but fish seemed happy back then? since then the levels naturally lowered since I stopped doing small daily water changes with ammonia-containing Instant Ocean salt water.

I have been using Seneye on and off for many months and it has been the first time I saw non 0.001 ppm free ammonia levels - I also started to add trim to ammonia recently.

Does the fact that ammonia persisted at these 0.05 ppm free ammonia levels for hours means that that I have inadequate biological filtration?

The tank has been running for 6+ years but I had few fish and easy corals so recently it has been very hands off ....
 
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Maga18

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a week or two ago, but from a very reputable store

Also the fish I added recently died second and seemed very happy just a day ago

I suspect something chemical - can they convulse from parasites? the only fish I saw dying got some kind of seizures (?)

I have been also working on the frags I probably turn pumps off for a bit, but when the second fish was dying they were on ....

Also the tank was very lightly stocked - only flame hawk, file fish (smallish medium) and a fire fish goby In 65 G with mature filtration ...

On the other hand, Seneye has been monitoring free ammonia and even dissolved oxygen continuously, there was no ammonia spike and dissolved oxygen has always been good.
 

ReefingDreams

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a week or two ago, but from a very reputable store

Also the fish I added recently died second and seemed very happy just a day ago

I suspect something chemical - can they convulse from parasites? the only fish I saw dying got some kind of seizures (?)

I have been also working on the frags I probably turn pumps off for a bit, but when the second fish was dying they were on ....

Also the tank was very lightly stocked - only flame hawk, file fish (smallish medium) and a fire fish goby In 65 G with mature filtration ...

On the other hand, Seneye has been monitoring free ammonia and even dissolved oxygen continuously, there was no ammonia spike and dissolved oxygen has always been good.
Most all stores get their fish from the same wholesalers. Fish disease is pretty common, unfortunately. Yes, disease/dying can cause convulsions. I think fish disease is more likely the culprit here.
 
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Maga18

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Most all stores get their fish from the same wholesalers. Fish disease is pretty common, unfortunately. Yes, disease/dying can cause convulsions. I think fish disease is more likely the culprit here.

;( Could I also brought disease on corals? How long does it take from infection to fish dying?

is it more likely infection happened 1-2 weeks ago or should I suspect corals I added yesterday?

It is heartbreaking for Christmas, kids sleeping do not know yet ...
 

ReefingDreams

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;( Could I also brought disease on corals? How long does it take from infection to fish dying?

is it more likely infection happened 1-2 weeks ago or should I suspect corals I added yesterday?

It is heartbreaking for Christmas, kids sleeping do not know yet ...
Sorry for your losses. It was much more likely to be the fish introduction. Some diseases can take a bit of time to manifest. But it isn't out of the question it could have come in on the coral. But at that point, it would need to be something very virulent like velvet.
 
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Maga18

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Sorry for your losses. It was much more likely to be the fish introduction. Some diseases can take a bit of time to manifest. But it isn't out of the question it could have come in on the coral. But at that point, it would need to be something very virulent like velvet.

So I do not have to do a massive water change? Corals seems strangely OK but I was convinced it was something in the water, did not know fish disease could be so sudden.

I was planning to add some corals from this tank to a new tank I am setting up - but they can bring disease with them - is waiting 6-8 weeks enough before adding fish? I understand that dips and rinses are not 100% effective.

Now that I have an extra tank I will finally quarantine everything properly - how many weeks are needed for a proper quarantine?
 
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ReefingDreams

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So I do not have to do a massive water change? Corals seems strangely OK but I was convinced it was something in the water, did not know fish disease could be so sudden.

I was planning to add some corals from this tank to a new tank I am setting up - but they can bring disease with them - is waiting 6-8 weeks enough?
A water change won't hurt, but I don't think it will do anything for you aside from usual benefit of maintenance. I'd target 8 weeks, with 6 being minimum. You'd need to be fishless for that entire period for that to be effective. No host, no parasite.
 

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I'm really sorry to hear about the challenges you're facing with your tank. It's never easy when unexpected issues arise. From what you've shared, it sounds like you're taking a thorough and thoughtful approach to troubleshooting.

The sudden deaths and changes in ammonia levels are definitely concerning. It's good that you're considering the possibility of impurities in the Kent Magnesium, and I agree that doing a water change with the Tropic Marine salt is a good step.
 
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