skinny kuhli and chinese butterfly loach

[sebastiansosin]

Two weeks ago I noticed some white spots on a guppy and I have done a 7 days 28 degrees treatment with Sera Costapur. I have done this treatment before and it went quite well. After the treatment was finished, I have noticed that one of my Gastromyzon (probably scitulus) became very skinny. I did check the water parameters and there was high concentration of NO3 and amonia.
I did large water change and quarantine the fish. Two days after I have noticed a very thin kuhlii, very weak, with no other external symptoms. Sometimes it was not able to stand properly, was just laying on a side. Sadly, both fish have died, they were not feeding at all or very little. I know that the butterfly needs cooler water than what I had during the treatment.

Yesterday I have noticed something else: one of the remaining kuhliis : it was very active as usual but it lost most of its colors. I fed them all and in a few moments he regained his normal color. Could it be that the fish was hiding in it's cave and because of the darkness it turned whitish?

Current water parameters:
pH:7.5 (untreated tap water has pH around 8 )
kH: 5
gH: 13
NO2: 0
NO3: 25
NH3-NH4: 0

Can someone help me with my problems?

[Diana]

I suspect the fish had more than they could deal with and the stress ultimately killed them.

Ich
Medication
Ammonia
Nitrate
temperature change, especially for fish that prefer lower temperature.
low oxygen because of the warm water and possibly Ich in the gills.

That is 6 different things coming at the fish all at once.

Here are some tips to avoid this sort of thing, but may involve some trade off of stresses.

Quarantine new fish in an isolation tank so they will not introduce Ich to the main tank.

Treat with the medicine that is safe for delicate fish. Some meds can be dosed at half strength, some should not be used at all. Many medicines kill the nitrifying bacteria. Be ready for this and have more bacteria ready to add to the tank as soon as the medicine is cleared. (I think Tetra Safe Start is available in the UK, look for Nitrospiros in the ingredients) Do LOTS of water changes while treating so that you are removing as much Ich as possible, as well as keeping the water conditions as good as possible.

Salt treatment is a different stress than medications, but does not kill the biological filter.

Keep fish together with tank mates that all thrive in similar conditions. Do not mix warm water fish (Kuhlies) with cool water fish (Hillstream species) When an emergency happens there is no room for any variations, you are likely to lose one species or the other. If you keep a cool water tank, centered on their optimum temperature and a separate warm water tank then the temperature could have been raised a few degrees in each tank, but not go higher than the optimum temperature foe the cool water fish.

Keep the gas exchange rate high by increasing aeration in the tanks when you need to raise the temperature. Adding an air bubbler, a power head, or lowering the water level so the water returning from the filter splashes a little can all help.

[sebastiansosin]

thank you for your reply. The stress was my first guess and I hope it is the correct one... don't like to add medicine to aquarium, no matter how "safe" the producers say they are.

I found out too late that the butterfly loach needs colder water. They seem to tolerate 25-26 Celsius without problems, even getting fat (almost doubled their size since I bought them)...but all the ammonia/NO3/Temperature/itch treatment were too much for these tiny creatures.

At least now the water is recovering and I have added an air bubble thingy on the filter return pipe so now my only butterfly enjoys more powerfull water jet with bubbles.

Again, thank you for the answer and if someone knows anything about kuhliis changing (losing) color and then turning dark again, please let me know. He seems really ok but I am scared.