Fish death 12hrs after refugium maintenance

[Drpuppers]

New to the hobby but have no idea what went wrong. Wanting to understand what happened to not repeat this mistake.

I have a 13.5 fluvol tank with marco rock and crushed coral. Tank has been running now for 3 month. So very new still.

First chamber
Filter is standard blue white filter pad, chemipure elite, media stones that came with set up.

Second chamber
Cheato refugium

Parameters before water change
PH 8.1
Ammonia 0
Nitrite 0
Nitrate 10
Salinity 1.025
Temp 77
Alk 7.1
Phos .1

The 2 clownfish, few snails, hermit crab, feather duster, zoas and a small piece of green monticap that randomly came with my zoa order. All acting the same as last week.

Preformed a 10% water change following same steps as previous times.
using RODI water that before salt read at 0ppt.
PH 8.2
Salinity 1.025
Temp 75

Only thing different this week was I removed a chunk of cheato as it had filled the back of the tank. As well some brown algae had begun building up.

Parameters after water change
PH 8.1
Ammonia 0
Nitrite 0
Nitrate 0
Salinity 1.025
Temp 76
Alk 7.4
Phos .07

No issues observed the rest of the night. Water change was done at 22:00.

The next morning at 07:00 both clownfish where found laying on their sides on the bottom of the tank with excessive breathing.

Immediately tested water parameters
PH 7? lower then lowest colour reading
Ammonia 0
Nitrite 0
Nitrate 0
Salinity 1.025
Temp 77
Alk 7.0
Phos .24


Did 20% water change to try boosting the PH to 7.8. Worried a larger jump would further harm the fish.
Also moved all return pumps to cause significant surface agitation thinking maybe o2 depletion.

Both fish were dead by 11:00.
However, all snails, hermit crab and feather duster show no change in behaviour.

Zoas still closed and green monticap turned brown.

is this my doing with the refugium agitation that I missed a safety precaution that would casue such a PH drop? Or is there something I’m missing here that would seem to not impact inverts but kill fish and agitate soft corals?

 

[Fish Fan]

Welcome to Reef2Reef! And sorry to hear about your Clownfish.

I'm not an expert, but it sounds independent of you removing the Chaeto. It may have been a fish disease that was kept in check, until it suddenly appeared, though any symptoms may have been very hard to notice. I think that typically when you see two fish die like that, but your inverts are fine, it points more to a fish disease than poor water quality.

I'd double check that last pH test, 7 seems way low given your salinity.

 

[Pistondog]

Removing chaeto may have disturbed detritus, perhaps causing a bacteria bloom which depleted O2. I run an air stone in my aio as i dont think it gets enough gas exchange.
Low ph might be due to excessive co2 from bacteria (and fish).

 

[Fish Fan]

Removing chaeto may have disturbed detritus, perhaps causing a bacteria bloom which depleted O2. I run an air stone in my aio as i dont think it gets enough gas exchange.
Low ph might be due to excessive co2 from bacteria (and fish).

This is a very good reply. But wouldn’t the fish be gasping at the surface rather than laying on the bottom gasping if this was low O2? Thanks for your help here!

 

[Pistondog]

This is a very good reply. But wouldn’t the fish be gasping at the surface rather than laying on the bottom gasping if this was low O2? Thanks for your help here!

I dont know the answer to that.

 

[Tamberav]

This is a very good reply. But wouldn’t the fish be gasping at the surface rather than laying on the bottom gasping if this was low O2? Thanks for your help here!

When they are so asphyxiated that they can no longer swim, they will lay on the bottom gasping.


However, a bacterial bloom that bad would probably be visible by milky colored water.

 

[Fish Fan]

Thanks for your help guys!

 

[Drpuppers]

When they are so asphyxiated that they can no longer swim, they will lay on the bottom gasping.


However, a bacterial bloom that bad would probably be visible by milky colored water.

The water was a bit cloudy, I was thinking I just disturbed the water with the water change and it was taking longer to clear.

So yeah I guess if inverts aren’t as sensitive to the o2 depletion and the sudden drop in ph would be the irritant that kept the zoas closed and browned the green monticap…

dang that’s a really stupid mistake, so this is anytime I have to maintain the cheato?
should have just put them into the new salt bucket water. I didn’t have enough for a full tank change since I just had done a water change and hadn’t time to refill the RODI water.

So I have a temp controller that sounds an alarm if there is a problem. Is there a similar thing for PH automated testing?
With a small tank I feel like I need real-time updates on it to stay on top of this.

Or is there a better aeration method for small tanks that I should be using

 

[Pistondog]

Better aereation!

Edit
I use an air stone but there might be better methods for you

 

[Drpuppers]

Better aereation!

Edit
I use an air stone but there might be better methods for you

Would it be better to undo the refugium and instead replace with a skimmer? Or just install an air stone in the back of the tank?

My hope was to have a mandarin dragnet in a year after establishing the tank more. So the main reason for a refugium was copepods. Or is that not attainable

 

[Pistondog]

I think it would be a challenge to keep enough pods in your tank for a mandarin. But, you can get mandarins that eat frozen foods.
I Would just add the airstone into the return chamber.