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Aquarium Disaster

S

Serenade4

Member
Joined
6 Apr 2021
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25
Location
Prestwick
Hi - looking for any advice please. I currently run 3 tanks, the oldest of which is a Fluval Roma 125l established 3 and a half years ago.

My usual maintenance regime is a 25% water change and filter clean every 2 - 3 weeks. Last session being Sunday. Before each session I check the water. For some reason on the Roma the ammonia had spiked and the pH dropped to about 6. I did a slightly larger water change than usual, all seemed OK in terms of water parameters and then on Monday morning 15 fish were dead and the remaining few have also now passed.

Running a water test now shoes Ammonia back up to a really high 2.0 on NT labs scale, 0 nitrite and 0 nitrate. Ph is about 6.

Fish were a mix of rummy nose tetras, platies, corydoras and one bristlenose. It is well planted with amazon sword, crypts, anubias, ferns etc. No Co2 injection and there never had been.

My other two tanks, 34l and 200l fluval have no issues, ammonia is 0. Exactly the same routine is followed. Water is treated with Seachem Prime before being put back in at water change and temp matched.

Has anyone experienced this horrendous event? Any idea what could be the cause?

Also I don't really want to give up on the tank but should it be a complete strip down, replace all substrate, hardscape, plants, filters etc?

Any help/pointets much appreciated?
 
Sorry for your loss.

It sounds like something in your tank died and was decomposing causing the ammonia spike. If you didn’t remove it then after a water change the ammonia would just increase again.

It’s a bit of a risk of a well planted tank. I often think when I clean my tank that if something died behind the hardscape, it’s unlikely I’d know about it.

I don’t think a full strip down is required but a good cleaning is worth doing. Find the cause of the ammonia and remove it The plants will consume any left over anmmonia and decomposing material. Large water change and monitor water quality like you would a new set up before adding any livestock again.
 
Serenade4 said:
I currently run 3 tanks, the oldest of which is a Fluval Roma 125l established 3 and a half years ago.
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Assuming this event happened in the Roma tank only and you run the 3 tanks similarly it’s probably fair to conclude that something like what @simon_the_plant_nerd describes above happened. However, in a densely planted tank (125 L) it’s rather unlikely a dead tetra or two (a large fish is a different story and you would have noticed it for sure) would cause a huge ammonia spike… so something else might be amiss. Could you post a picture of the tank?

What kit are you using to measure ammonia?

Cheers,
Michael
 
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Agree with Michael also if you have a ammonia detoxifier like prime you could use it and do daily/every 2 days water changes until filter catches up and also look for any possible cause.

I have heard of old tank symdorum but I think that is related to high levels for nitrates which you tested and it was zero so not sure
 
Scaperinc said:
Agree with Michael also if you have a ammonia detoxifier like prime you could use it and do daily/every 2 days water changes until filter catches up and also look for any possible cause.

I have heard of old tank symdorum but I think that is related to high levels for nitrates which you tested and it was zero so not sure
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Q
 
Thanks for all the comments so far. I've attached a couple of pics but the tank has been messed around a bit over the last couple of days as I made sure there was nothing left dead inside.

Would the high ammonia cause the pH to drop so low? It is the NT Labs text kit which I use.

When cleaning I don't tend to disturb the substrate. I don't vacuum it at all.

I'm relieved that a full strip down may not be needed although from what I have learned over the few years since setting this one up, was my first tank, the substrate could better. It's just really sand and gravel.
 

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It's a very unusual thing to happen in an established planted tank that's getting regular maintainance.

In old tank syndrome you build up nitrate/ammonia and a lack of kh becomes an issue, ph drops - then if you do a sudden water change shoot up the ph and turn ammonia from ammonium (less toxic) to ammonia (toxic) causing deaths.... but the issue is the tank has gone a long time without water changes not if you are doing 25% weekly.

I don't think the tests necessarily diferentiate between ammonia/ammonium, so it could have been an element of that - the water change raised ph and made the ammonia more toxic, hense the sudden deaths. By even that doesn't explain why it was there in the first place.

What's your gh/kh - just roughly? Soft water is more prone to pH swings.

Do you have a small child/extremely clever cat or over enthusiastic partner that could have dumped excess food in without you catching it? A large male bristle nose could maybe be big enough to cause a spike if he went first - did you see him alive at/after testing?

I wouldn't break it down completely unless you want to reset, just get things back on track and do a few big water changes.
 
Thanks Tam.

Can rule out the cat/small person chances. Male bristlenose was one of the last to pass, after testing.

Our water here, in Prestwick on west coast of Scotland, is noted as being soft on Scottish Water website so that may be something.

Unbelievably, as I sit in front of the aquarium typing this, having rooted about and moved the hardscape to try and find all the dead bodies several times for ages, as I couldn't account for 3 rummy nose and just assumed they had vanished, they have just swam past!!

So next question, do I move them to my stable 200l tank or leave them while trying to stabilise this one?
 
Serenade4 said:
So next question, do I move them to my stable 200l tank or leave them while trying to stabilise this one?
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Pros - the other tank is stable and you don't know what caused the issue in this one so hard to guarentee it's ongoing conditions, cons they could be suseptible to illness after the stress and catching them up/moving is more stress, and catching them back out of a 200l may be fun. Up to you really. If you leave them in I'd add an airstone and staying on top of water changes is more important, if you take them out then you could potentially just let the tank stabilise itself - the plants/filter will eventually use the excess ammonia.
 
Decided, on balance, to leave them in the current tank. Have added an air pump and will carry out frequent water changes. Add more plants too?

I've taken out the moss balls which certainly were not in good health.

Many thanks again for all the help.
 
Serenade4 said:
Running a water test now shoes Ammonia back up to a really high 2.0 on NT labs scale, 0 nitrite and 0 nitrate. Ph is about 6.
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Not sure if anyone noticed this above, but even a TAN at 2.0 ppm with a pH at 6 (assuming 24 C) the free un-ionized ammonia (NH3) would only amount to 0.001 ppm. - ways below lethal levels. Other possible causes for this could be release of buildup of certain traces in the substrate such as Copper or Zinc.. which becomes more toxic at lower pH... This is a phenomenon that is often overlooked in old tanks.

Cheers,
Michael
 
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MichaelJ said:
a TAN at 2.0 ppm with a pH at 6 (assuming 24 C) the free unionized ammonia (NH3) would only amount to 0.001 ppm
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I’m interested to know how that is calculated. I know NH3 is toxic and NH4 much less so but how does the PH and temperature affect the ration between the two when a TAN value is given?
 
"buildup of certain traces in the substrate such as Copper or Zinc.. which becomes more toxic at lower pH... This is a phenomenon that is often overlooked in old tanks."

Thanks Michael, if I get the pH back up is that sufficient to control those traces or is the substrate which will be four years in the tank come August had its say?
 
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