Mandarin Fish Dying from Unknown Illness


New Member
Last week I got a Royal Gramma from my LFS. After drip acclimating, I put the fish in the tank and it immediately went into hiding. I did a 50% water change 3 days later and I know the fish was still alive then. A couple days after this I saw my hermit crabs eating the dead Royal Gramma. About a day before this I noticed my Mandarin fish was gasping for breath. He was still eating and swimming around at this time so i figured he was just stressed from the water change. After the Gramma's death his gasping got worse, he stopped eating, and I noticed a couple semi transparent skin tags on him. When he continued to get worse I took him and my small clownfish out of my main tank into a quarantine tank. The clownfish seems to be doing fine but the mandarin has looked on the brink of death for several days. I finally decided to do a freshwater dip (I'm aware this is bad for the mandarin due to their slime coat) because I suspected gill flukes and figured he was going to die if I did nothing, so why not try. I did not see any parasites falling off him in the water. He is now back in the quarantine tank and is in bad shape. I figured he was a goner a couple of days ago. At this point I just want to figure out what is wrong with him so I can have a chance to save my clownfish if he falls ill. The mandarin is particularly hard to diagnose because his vivid coloration and thick mucus makes it hard to see bumps or spots on his skin. I did not notice any sort of bumps (ick or velvet) on the Royal Gramma before it died, but it also spent all its time hiding in the live rock so I never had a great look at it. The mandarin fish now has white in the iris of his eyes, they are not cloudy but a bright white. He is gasping at the bottom of the tank and doesn't look good. The freshwater dip did a number on his slime coat (again I was aware this would happen). Can anyone think of a diagnosis for him? I really don't want to lose my clownfish too.


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Well-Known Member

to ReefSanctuary, a real Sanctuary of reef forums, with lots of very nice members

Start a tank thread & share your tank with us so we can follow along, we love pics

Hopefully some can advise with some ideas to save your fish... diseases are my weakest suit...

if it's any help... our stickies in this forum are great & may be of some help... they were written by Lee Birch.


Well-Known Member
I sure does sound like something wasn't right with the water change. Here are a few questions on that -

Why did you make a 50% water change? It's a very large amount.
How did you mix your new SW?
Did you match temp and SG carefully?
How large a tank are we talking about?

Another possible thing to check for is disease. I do seem some white spots in the picture, but I can't tell if they are on the fish or just something on the glass. It's very easy to bring in diseases with new fish. It is also possible that the tank already had parasites in it, and the stress of the water change brought it out in the open and active. Look at all your fish for SW ich and velvet. SW ich looks like small white dots. Velvet looks like fine gold dust, and that's why it's also called gold dust disease.


New Member
I did a 50% water change because I wanted to remove the sand bed and have a bare bottom tank. I took 50% of the water out and put it onto clean buckets. Then put the fish and corals in a large bucket with an airstone and the live rock in a different bucket. I then emptied the remaining water and took out my sand bed. I then poured the old and new water back into the tank then placed the live rock back in. I drip acclimated the fish and corals before putting them back into the tank.
The tank is 12 gallons. All the fish are very small. The mandarin and clownfish had been doing fine in the tank for several months together before I added the gramma. To feed the mandarin I have 8 separate 2.5 gallon buckets of tigger and tisbe copepod cultures. I also hatch baby brine shrimp for the mandarin. I do not think feeding was the problem, he was very fat before he got sick and was always picking at the glass and live rock. I do a 25% water change twice a week on the tank.
The white spots you see are air bubbles. He doesn't have any white spots on him. I did see clear bumps on him when he was in the main tank, this is what finally sparked me to take him out and put him in quarantine. It's rather difficult to tell if the bumps I saw were actually bumps or just thick slime from his coat.


Well-Known Member
You have another issue here. Your tank is way too small for more than 1 small fish. By going up to 3, you were grossly overcrowded.

By the time you take a 12 gal tank and add live rock, you down to under 10 gal of water. With SW fish you want about 1 inch of fish per 5 gal of water, or about 2 inches of fish in a 10 gal tank. Typical sizes for the fish your talking about is about 2 inches each, but you also need to allow room for growth.

If you want that many fish consider upgrading the tank to something a lot larger.