So i came home this afternoon from work to find my entire colony of leopard fish dead - a couple still wriggling - but all have ultimately died.

Now im no stranger to death when it comes to fish it can sometime be a bit of a numbers game and when you have ALOT of fish you tend to see it a little more frequently as the generations come through but not usually in these numbers.

So this tank is a well cultured tank - its housed wcmm and leopards for about four months now of various sizes - but previously housed guppys for 9 months - mostly well grown fish. its a 300l and had about 100 leopards mostly well grown adults and 20 or so wcmm. Its gets water changes twice a week and i feed live food - has alot of moss and a thick layer of riccia and brazilian pennywort.

Its strange because all of the wcmm are uneffected but not a single leopard remains standing, also strange because this morning at 7am (as i run my fishroom backwards to my daytime) when i put them to bed, everything was good! infact i had noticed a few day old fry. Some of these girls id had for 4 years or so, so were probably on their way out anyways - but another weird thing is about 50% of the lush green riccia that usually floats on the surface had turned brown grey and kinda slimy. This is only about 7 hours after id left them this morning.

Ive pulled it all out and done a 90% water change, taken all the dead bodies out and left the wcmm as they seem fine but im wondering if anyone could figure out what may have occurred? foul play? I've not ever really had a mass extinction event accept when i was 13 with my first tropical fish tank and boiled it because there were no thermometers on those heaters then.

Let me know if you've got some idea's

Cheers

Wow, that sounds really awful. Did you have a few leopards tucked away somewhere else to re-start with?

Trying to think of something that would kill off just the leopards and leave the WCMM, but very difficult to imagine. Maybe some sort of filtration issue, and you got there just in time before the WCMM succumbed as well?

Disease seems unlikely, and any 'chemical' would presumably have taken out everything in the tank.

Good luck with finding and fixing the problem.

Ammonia spike?

Is your tank heated, if so check the temp

I was thinking temperature too. WCMM cope with a wide range of temps but leopardfish don't.

I was thinking temperature too. WCMM cope with a wide range of temps but leopardfish don't.

I'd be inclined to doubt temperature is an issue, it's been much cooler the last week or so. I'd think if getting too hot was the cause I'd have expected them to have died a month or two ago.

Sad story

- Big dead hidden bristlenose in there that caused bacteria to explode?

- Power-cut that stopped the filter and when the power came on again flooded tank with dead bacteria and whatever happens to them and poo under anaerobic conditions?

Cheers,

JaSa

I was thinking more a faulty heaterstat than room temperature.

Are you adding excel?

If the riccia is turning up its toes I would expect a temp spike. maybe the heater stuck on for only a while and then turned back off?

pH crash?

Agreed Blueether. When I thought about what might have happened I thought what might have killed the riccia rather than what killed the fish.

There is no reason to have a heater in that tank and nor has it been mentioned. So was there a heater?

Would you like some replacements?

I'm sure I will send a parcel again to a person we both know in Wellington at some stage