Unexplained deaths...

[alanchown]

My 200L tank has always been well maintained. EI ferts, CO2, and weekly 50% water changes. That is until about 4 months ago, I lost 50% of my fish due to overdosing CO2, and it has been subsequently neglected for 4 months due to family illness.

2 weeks ago I got the tank into good order. I chucked all the unhealthy and indeed healthy plants. Cleaned filters etc. Substrate is the original, JBL aquasoil Now replanted, plants going well. Added a dozen cardinals and a few very small angels. Water parameters are all good.

Only problem is I'm losing my original survivors,5 fish in the last 5 days and my last hatchet about to join them. Absolutely no indication of any fish Ill health, no fungus, feeding fine, and then dead. The hatchet is the exception and hasn't looked well for a couple of days, but no external indication of anything wrong.

I have treated today with an anti bacterial medication. Any ideas what may be the issue? New fish from very reputable suppliers.

Alan

 

[dw1305]

Hi all,

2 weeks ago I got the tank into good order. I chucked all the unhealthy and indeed healthy plants. Cleaned filters etc.

Could be a water quality issue as you've reduced your biological filtration capacity and disturbed the substrate.

New fish from very reputable suppliers.

I'd would still have quarantined them if I could.

cheers Darrel

 

[alanchown]

I was thinking along the lines of the disturbed substrate, water was black for a good few hours. Having said that, that was 2 weeks ago.

Unfortunately I have no quarantine facility.

Alan

 

[sciencefiction]

After every action, there is a reaction, or so I have found out via experience. There is a delayed onset between mistreating fish and the consequences to follow. Most fish, unless the circumstances are extreme, survive the worse but break down with diseases down the line or die sooner rather than later due to compromised immune system.

 

[alto]

Sorry for your losses

New fish needn't be "ill" - just different "normal flora" than the fish you've had at home these last months

As sf mentions, all the recent upheavals may've stressed your original fish - stress significantly suppresses fish immune system - followed by exposure to new (potential) pathogens

Rather than adding antibacterial meds, I'd just do daily water changes, ensure good oxygenation

Given the lack of symptoms (& time frame) I'd be surprised if the issue is bacterial

 

[alto]

If you haven't already, I'd rinse the filter media, switch out the mechanical filtration (if filter pad/floss)

 

[alanchown]

Filters all been cleaned, all fish feeding fine, even the hatchet looked OK last night. 50% water change as well at the weekend, so lets see what happens....