Problem after rescaping

[Keebs]

Hi helpful people and thanks in advance for reading.

My 150L community tank has been running for 6 years without a problem.
5 days ago I had to re-adjust some wood hardscape that had shifted which involved disturbing the gravel substrate at the "heaped" end.
Aquasoil underneath but I don't think I disturbed it that far down.

2 days later one of my Cory Sterbai was obviously struggling to swim properly, sometimes floating upside down, had darkened, gone very thin and was breathing heavily. No spots etc.
All other residents seemed fine.
Next day it was in such a bad I way I had to euthanise.
The same day I noticed the very occasional bit of "flashing" from 2 or 3 of the other Cories and my Mystery Snail had floated up to the top and locked itself in.

Figures below but as all water parameters were the same as usual over the last 4 days I have done 3 x 40-50% water changes with vacuuming in case there was anything nasty in the substrate.

Today most of my Cories look a little lethargic, one in particular similar to the now dead one.
No signs of spots or fungus on any of the fish at all but the Mystery Snail usually so active, is still alive but done nothing for days.
All other fish look fine but with the odd fin-split here and there.

Obviously something bad has happened to the water and possibly the stress of this has caused a flare-up of something - but what?
Never had a problem before so a bit stumped.

150L tall planted tank, Aquasoil topped with gravel/sand.
External 850L/H filter.
Temperature 25
Ammonia 0
Nitrite 0
Nitrate 10ish
KH 18 (as normal here)
GH 24 (as normal here)
PH 7.5 dropping slowly to 7 during 8 hr CO2.
All the above parameters have been stable throughout, matched previous, and there was no ammonia spike after rescaping (I was paranoid and checked 4 times, 3 hours apart after!)

Residents

1 Golden Apistogramma
1 Duplicarious Cory
6 Sterbai Cory (now 5)
6 Julii Cory
9 Neon/Cardinal Tetra
8 Blue Emporer Tetra
6 Ember Tetra
5 Amano Shrimp
2 Nerite Snail
1 Mystery Snail
1 Papua Bluberry Snail
1 Green Torpedo Snail


Ich?
Bacteria?
Parasites?

Everywhere I look online the symptoms vary and overlap!
Hopefully I get a more context- specific answer here.

Thanks again for reading.

 

[Keebs]

Been watching intently for the last couple of hours and it really does just seem to be the Cories & Mystery Snail affected. Everthing else seems to be acting and feeding normally.

 

[MaloK]

That makes me think about hydrogen sulfide poisoning. Bottom dwellers are more likely to have higher exposure.

How thick is your substrate ?

Any bubbles came up when moving the wood ?

Any rotten egg smell from the vacuumed water ?

 

[Keebs]

Hi & thanks for the reply

It's 4-5" deep at the point I was disturbing.
Don't remember any smell but it is possible.
The deep tank with a rim all round makes it difficult to see what you're doing so I wouldn't have seen bubbles anyway.

Presumably this would this be a one-off damage kind of scenario?

 

[MaloK]

That is a pretty thick layer, habitually 2-3 inches are more than sufficient.

Next time you do a vac job, look out for sulfur smell, just in case.

If it does, doing deeper cleanups will help. But I can't say that it will be a one time only occurrence.

If the inherent factor that causes the buildup is not addressed, it will slowly come back.

 

[Keebs]

Sorry just to clarify - that's total depth to the glass bottom, only 2" (at the top) of that is gravel, the rest is aquasoil.
It's the end the filter uptake sits so I always make sure that bit is vacced.

If there was a realease then it's very possible it built up under the wood and/or the large rock that was propping the wood up.



Having changed about 80% of the water since, is there anything else I can do for the suffering fish? (Other than maintain good conditions for them to heal again)?

 

[MaloK]

Yes, I agree, most of the time it builds under larger pieces of decor.

If it's the case. You had a rapid reaction, and your cleanup and water changes did good.

But your description of the symptoms fits the bill @ 100% for me. Struggling to swim, floating upside down, darkened color, breathing heavily.

There's only the "gone very thin" statement that seems out of context. Are the other having the same ?

 

[GaryE]

It could be chemical release, but could also be bacterial. The affected fish are the ones who snuffle through the substrate...

I think you may have the cause in terms of the action that released to toxins or pathogens, but what was released may be much harder to figure out, if you ever even do.

Watch that Apisto.

 

[Keebs]

There's only the "gone very thin" statement that seems out of context. Are the other having the same ?

Only one other Sterbai is looking a bit emaciated, the other Cories generally look OK, just their behaviour is off to varying degrees. Some of both Sterbai & Julii are flashing now and again and looking at bit red in the gills.
Maybe that one was a weak fish anyway but yes it does seem to have emaciated quite quickly after the event.

A few mins ago the Mystery Snail woke up, went 4" up the glass looking like it was feeding for a few mins, fell off and went back into its' shell again. That thing is usually roaring round the tank.
All the other snails & shrimp feeding normally

 

[Keebs]

It could be chemical release, but could also be bacterial. The affected fish are the ones who snuffle through the substrate...

I think you may have the cause in terms of the action that released to toxins or pathogens, but what was released may be much harder to figure out, if you ever even do.

Watch that Apisto.

Thanks for joining
Let's hope it's released and gone now

The Apisto looks and is behaving same as ever, any gill-reddening would be obvious with that one, it's mostly white.

 

[Keebs]

Managed to get a shot of the worst affected Sterbai.

 

[Keebs]

And one of the others with reddening.