Mistake

[Danielm]

Guys. Bit of a disaster and trying to diagnose.

I run a 250litre sumped system (200l display /40l sump) - I run pressurised C02 into the sump.

I came home last night and my return pump had stalled- at this point I did not pay too much attention to the fish. I restarted it and left the room. 5 mins later all the fish are at the top of the tank, or swimming like they are intoxicated.

For about an hour I had 6 Corys all on their backs, a pair of rams being blown about by the return and tetras all I’ve the place

My only reasoning is that as a result of the Return failing, the C02 going into the sump made that water highly highly saturated with C02. (No usage by plants in display, no loss through water movement etc.) When I put the pump back on, that water all went into the display very quickly and caused a massive shock....

I generated as much water movement as I could and things seemed to get better over about an hour....the corys started swimming again and the rams are still here this morning...lost all my tertras it would seem however....

Does my reason for this add up? Just want to make sure I have not missed something before I start the ‘clean-up’ and then think about restocking.

Thanks

 

[Edvet]

Depending on how long the system was down, and your configuration, there could have been oxygen depletion in the sump too, possibly leading to toxins/toxic metabolites. These might have to do with fish deaths.

 

[Hendre]

Agreed with the above. The O2 would be depleted, and the co2 levels could have impacted the fish as well. Sorry to hear 🙁

 

[ian_m]

Not sure what caused you issue, but my tank went for about 3 days with no power when I was away one Xmas.

The sudden deaths could be caused by temperature difference of the unheated sump water suddenly going into the tank.

Also not sure about oxygen depletion either as one Xmas we had a substation neutral fault that tripped all my estates houses RCDs. Fault was corrected in an hour or two according to neighbour, but we were away and not able to reset the house RCD. Tank was 17'C when I got back, filter fine, plant & fish fine once all warmed up. So filter left off for 3 days.

 

[Zeus.]

Sorry to hear the news🙁
With my duel CO2 injection setup and a big pH drop over 1.0pH i am able to get the pH drop in under 45mins np. As a result when the lights come on some fish are always at the surface gasping a little for 15-30mins then they all resume normal depths in the tank. I have reduced the pH drop recently, but before I did reduce it if I feed the fish before CO2 went off the fish got excited as they do OFC and a few tetras in their increased activity would go belly up in the current for a short while then recover. Which sounds similar to what happen to your tank when the sump water with high [CO2] hit the main tank.

Maybe two pumps on independent returns would suit your setup better in case a pump stalls again! Or wait for the sump to degas it's CO2 before starting pump next time if the CO2 has been on for some time!

 

[Danielm]

Maybe two pumps on independent returns would suit your setup better in case a pump stalls again! Or wait for the sump to degas it's CO2 before starting pump next time if the CO2 has been on for some time!

Two pumps not gonna work as the return are built into the system, but yes.... will need to degas the sump (or do a sump only water change) - just did not enter my head yesterday . Doh

 

[Zeus.]

Two pumps not gonna work as the return are built into the system, but yes.... will need to degas the sump (or do a sump only water change) - just did not enter my head yesterday . Doh

Sump only change would be quick too

 

[Mihai Varban]

If your sump, which I assume holds a lot of filtration media, had an oversaturation of CO2, I'd assume a lot of your aerobic bacterial colonies were killed. This would result in an ammonia spike AND hight TDS AND pH change AND toxins AND low oxygen water being pumped into your tank at once. This means that your sump will need time before it can properly filter again and your fish are shocked. If it were my tank, I'd immediately put in some air stones while I tested the water to confirm. Then I'd follow up with a few frequent water changes while watching things like a hawk, removing dead fish etc. I feel for you as this is such a perfect storm of bull**** to hit your tank and totally beyond your control. Please use this as an opportunity to learn and maybe make the changes you've been planning on your tank.

 

[Zeus.]

If your sump, which I assume holds a lot of filtration media, had an oversaturation of CO2, I'd assume a lot of your aerobic bacterial colonies were killed. This would result in an ammonia spike AND hight TDS AND pH change AND toxins AND low oxygen water being pumped into your tank at once. This means that your sump will need time before it can properly filter again and your fish are shocked. If it were my tank, I'd immediately put in some air stones while I tested the water to confirm. Then I'd follow up with a few frequent water changes while watching things like a hawk, removing dead fish etc. I feel for you as this is such a perfect storm of bull**** to hit your tank and totally beyond your control. Please use this as an opportunity to learn and maybe make the changes you've been planning on your tank.

I agree with your comments esp if the sump was designed with a reactor media section, the lack of flow through that section would of resulted in very high levels of [CO2] and increased pH drop which could result in killing bacteria.
However with the lack of flow in the sump the [CO2] and pH drop would be localised to that 'reactor' section of the sump IMO
I make the above assumption based on CO2 diffusion rate in water being 10,000 slower than in air. As we need good turnover rates in our CO2 injected tanks to get the Distribution of CO2 the lack of flow and glass strips in the sump would surely result in only a compartment of the sump getting the high levels of CO2.
So the effect of such an event as the OP has had occurr would vary dependant on sump design and point of CO2 injection and the number of filter compartments also!
If the sump had a pre filter section the effect of no flow in the sump may not have affected the bacteria on the media as much which would speed up the recolonisation of the bacteria in the affected media massively IMO.

Do you have a pic or drawing of your sump design?