Second opinion on fish death wanted

[Shnetts]

the tank is new, about 6 weeks old. There’s 4 fish. Midas blenny, bangaii cardinal, randalli assessor and a baby chocolate tang.

Everything was normal this morning, I got home and it’s having a massive algae bloom. Didn’t think much of it. Turned the lights off and put a uv in. But I noticed my bangaii had passed and the tang was on his way out. Heavy breathing, laying on the sand. Both were fine and ate this morning. I put the bangaii in fresh water to see if maybe flukes but nothing. And no other viable signs. I think it’s from the algae starving out the oxygen in the tank.

For anyone wondering my water tests were the following
Ammonia = 0.01
Nitrate = 14
Phosphate = 0.13
Salt =1.025

 

[exnisstech]

What do you have for flow to help with aeration? I would add an air stone power head or something since I think you may have answered your own question with this statement

I think it’s from the algae starving out the oxygen in the tank.

 

[Shnetts]

Yeah I just put an air stone in and aimed my return pump at the surface.

That’s my best guess I was just curious if others had the same thoughts

What do you have for flow to help with aeration? I would add an air stone power head or something since I think you may have answered your own question with this statement

I think it’s from the algae starving out the oxygen in the tank.

 

[KrisReef]

A picture of the tank and the fishes might improve diagnosis

 

[snowy554]

the tank is new, about 6 weeks old. There’s 4 fish. Midas blenny, bangaii cardinal, randalli assessor and a baby chocolate tang.

Everything was normal this morning, I got home and it’s having a massive algae bloom. Didn’t think much of it. Turned the lights off and put a uv in. But I noticed my bangaii had passed and the tang was on his way out. Heavy breathing, laying on the sand. Both were fine and ate this morning. I put the bangaii in fresh water to see if maybe flukes but nothing. And no other viable signs. I think it’s from the algae starving out the oxygen in the tank.

For anyone wondering my water tests were the following
Ammonia = 0.01
Nitrate = 14
Phosphate = 0.13
Salt =1.025

Really sorry to hear this—losing fish unexpectedly, especially ones that seemed healthy earlier, is incredibly frustrating. Given your parameters, nothing stands out as immediately alarming, but a sudden algae bloom could absolutely impact oxygen levels, especially if it spiked during the day and dropped hard at night or with lights off.


The UV was a good call. Adding extra surface agitation (like pointing a powerhead at the surface or running an airstone temporarily) can also help boost oxygen levels fast in situations like this.


Keep a close eye on the remaining fish, and maybe consider running carbon just in case anything odd got into the water. You’re doing all the right things under tough circumstances—hang in there!

 

[vetteguy53081]

the tank is new, about 6 weeks old. There’s 4 fish. Midas blenny, bangaii cardinal, randalli assessor and a baby chocolate tang.

Everything was normal this morning, I got home and it’s having a massive algae bloom. Didn’t think much of it. Turned the lights off and put a uv in. But I noticed my bangaii had passed and the tang was on his way out. Heavy breathing, laying on the sand. Both were fine and ate this morning. I put the bangaii in fresh water to see if maybe flukes but nothing. And no other viable signs. I think it’s from the algae starving out the oxygen in the tank.

For anyone wondering my water tests were the following
Ammonia = 0.01
Nitrate = 14
Phosphate = 0.13
Salt =1.025

Starving out oxygen was my first thought but phosphates does not suggest at a high level.
Water: Are you using RODI water or tap water from the faucet ?

Additional light: Is this tank by chance at or near a window?

Phosphate: How are you testing phosphate? Normally with this level of algae, you will have a level of phosphate
When you found fish dead, was the mouth open or closed? Please post pics of overall tank using bright white light intensity

 

[MnFish1]

OK - so - some assumptions (correct if wrong - because I don't understand your post entirely)
1. By algae bloom you mean 'in the water' - as compared to on rocks, etc?
2. How can you tell its an algae bloom (less likely) than a bacterial bloom?
3. How big is the tank - its possible that the cardinal for example died - and that caused a down hill crash - though its quick for that - Its also quick for an algae bloom
4. You got all of the fish 6 weeks ago or so

So first as @KrisReef said - pictures would be helpful. Second - cardinals especially wild carry/are often infected by an iridovirus - and it may be a little long in your tank for this - but I wonder if it died (which can be sudden) and then started decomposing - leading to a bacterial bloom. Which lowered oxygen levels and continued the cascade.

Additionally, another disease - such as velvet flukes or ich may also be possible - depending if you QTd the fish.

Additionally 2 - it could also be some kind of toxin, or your pump stopped (power failure of some kind)? and that lead to low oxygen and death.

Your ammonia is slightly high - not enough to cause the problem - any more information you can give?

 

[Jay Hemdal Verified Community Expert]

the tank is new, about 6 weeks old. There’s 4 fish. Midas blenny, bangaii cardinal, randalli assessor and a baby chocolate tang.

Everything was normal this morning, I got home and it’s having a massive algae bloom. Didn’t think much of it. Turned the lights off and put a uv in. But I noticed my bangaii had passed and the tang was on his way out. Heavy breathing, laying on the sand. Both were fine and ate this morning. I put the bangaii in fresh water to see if maybe flukes but nothing. And no other viable signs. I think it’s from the algae starving out the oxygen in the tank.

For anyone wondering my water tests were the following
Ammonia = 0.01
Nitrate = 14
Phosphate = 0.13
Salt =1.025

Was the algae bloom made of the green free floating algae? Video would help.

If so, there are four possibilities:

Oxygen deficiency at night due to reverse phase photosynthesis. This would not happen with the tank lights on.

Some algae can release toxins….dinos mostly.

Whatever caused the algae bloom affected the fish. I rarely see green water algae blooms in marine tanks, I wonder what’s fueling it?

Completely coincidental - the algae bloom is unrelated to the fish loss. If the fish werent quarantined, they could have a gill disease.

 

[Mr. Mojo Rising]

What is the tank size? Its very odd to have so much algae in a 6 week old tank that it can kill fish, even algae takes time to grow. Need more info to find the real cause

 

[Shnetts]

Tank is 50 gallons. Definitely had some diatoms before hand but that was all

It has since somewhat faded overnight but I couldn’t even see through the tank when I got home.

 

[MnFish1]

Tank is 50 gallons. Definitely had some diatoms before hand but that was all

It has since somewhat faded overnight but I couldn’t even see through the tank when I got home.

It was most likely a bacterial vs algal bloom - since it came on so fast, and went away so fast.

 

[Shnetts]

It was most likely a bacterial vs algal bloom - since it came on so fast, and went away so fast.

Is that going to have the same oxygen deprivation effect?

My tang perked up for a hour or so after I put the bubbler in. But now he’s back to laying down

 

[MnFish1]

Is that going to have the same oxygen deprivation effect?

My tang perked up for a hour or so after I put the bubbler in. But now he’s back to laying down

Bacteria grow (use oxygen) much faster than algae. When the lights are on - algae will increase oxygen - when the lights are off algae will reduce oxygen. Like I said - It seems like you have oxygen under control. Have you rechecked your ammonia etc lately?

 

[Shnetts]

Ammonia is still 0

 

[Shnetts]

Will turning the lights back on increase the bacteria at all?

 

[Shnetts]

After laying down all day the tang passed

 

[Shnetts]

@Jay Hemdal @vetteguy53081 are you able to see anything notable from the photo?

 

[KrisReef]

@Jay Hemdal @vetteguy53081 are you able to see anything notable from the photo?

Clear eyes, clear/ clean body, no obvious disease indications, I would run carbon for possible toxin issues and make sure oxygenation is happening with water movement and skimmer / maker & airstone operation .

Otherwise, still a sad mystery

 

[Shnetts]

Clear eyes, clear/ clean body, no obvious disease indications, I would run carbon for possible toxin issues and make sure oxygenation is happening with water movement and skimmer / maker & airstone operation .

Otherwise, still a sad mystery

Is the black gills a sign of anything?

 

[vetteguy53081]

After laying down all day the tang passed

Fish a little thin and light inflammation at the gills. Often hard to determine once dead and when distress is seen, capturing a video will be of help