ok....
Since separating the tetras, I have lost another two fish, and a fungus appeared on the ornaments in the tank, so I guess I had some sort of fungal invasion in there.
Also, the two I lost were bettas, not something I particularly wanted to happen!
Yesterday morning I took the very dramatic action of putting all the fish into my little 2' tank and completely emptying the big tank and cleaning the whole thing out.
Bit of a squeeze in the small tank though... I ended up with 6
goldfish, 2 angels, 2 gouramis, 15 neons, three tetras, three danios, 2 plecs and 2 bettas, all trying to get on in a 15 gallon aquarium!
The immediate thing to do, was to get the big tank back into action as quickly as possible, so after taking 5 hours cleaning and boiling all the different bits, I managed to get it back in place, re-filling it with treated water using tetra AquaSafe and being very cruel, quickly heated it using the boiler and the tank heater, and transferred the 6 goldfish and the 3 danios into the clean tank.
Before you start, I know it hasn't cycled, but with the crowd in the other tank, I didn't have time for that luxury. I am just going to have to keep changing the water daily till it cycles with the fish in there. However, I also added tonic salts to the water this time, to make sure that any fungus that might have survived is taken care of. The tank temp is now at 30C, (I also did some reading and this is apparently the best cure for fungus), which the goldfish LOVE! I never considered the goldfish as enjoying warm water, but they love it, playing in the bubble streams and the
powerhead jet.
As for the other tank, i seems to be stable and the remaining fish have enough room for the time being. Luckily, they are all small at the moment, so there is enough room until the big tank is ready for them again.
For the future, I am getting a small tank for quaranteen this week, so that this problem won't occur again.
Thanks for all the advice. I think I've learned a few lessons here, not least, to ensure that the fish are well and compatible BEFORE I introduce them to a large tank, and not to buy too many fish too soon!
P.S. I also found out that the source of the infection was not the danios, but the bettas, that my partner bought from the local pet shop the next day. Out of the 3 she bought, all have since died. If I had the
QT the problem would never have arrisen, since they would not have been introduced to the community tank at all. Gives you a good reason to get a quaranteen tank, doesn't it!