Help! Dying loaches with white peeling "skin"

[chefkeith]

TDS is also not likely to cause this type of issue, unless the dissolved solids are toxic...

Hate to say it, but you're wrong.

Osmotic Shock
Symptoms:
Detachment of mucous membrane, fins appear to have been blown off, internal diseases become the consequences, increased vulnerability to skin diseases, gill and fin rot.

Causes:
When fish is transferred from water with high conductivity (high salt content) to water with low conductivity without an intermediate phase for adaptation, they suffer from osmotic shock. The fine cartilage joints in the fin rays can burst due to the high osmotic pressure. The fins fall off in large pieces and the fins are eventually infected with fungus and other bacterial infections especially when the fish becomes extremely weakened.

Treatment:
This is more of a case of prevention rather than actual treatment. Measure the conductivity between the water where the fish is and the water where it is to be transferred. The addition of mineral salt to the one with higher conductivity level will help minimize the chances of osmotic shock. Give the fish time to recover from the upheaval. Then, proceed to lowering the conductivity level to the desired level by doing small water changes over several hours.

http://www.fishforum.com/tropical-fish- ... 179/page5/

[Diana]

Great info, Chief!

I find that altering the TDS is safer done over a couple of weeks, not just a few hours. Whether I am moving the fish into harder or softer water I do it in small steps, a little change every few days.