I do 40-50% water changes weekly with never a problem. Difference is my tanks are much bigger (75, 125, 200 g) so the water change is much more gradual, it takes about an hour and a half on the 200 and 125). I think this is part of the problem, introduce your new water much more slowly.
Not a big fan of amquel+, the original amquel was much better IMHO. While an OD might have added to the problem I highly suspect it was not the main source. You should check the water parmeters of the water you are adding as well as the tank water. I know my tap water can very from 7.8 to 8.6 PH. Others here may never have this issue, it all depends on your LWTP. However, the most important of all the parameters when doing water changes is temperature!
I know there are lot of fans of everyones favorite dechlor, but in my expeirance nothing beats good ol' ST. Sure you might get a slight ammonia level (which would hardly be detectable and easily handled by your bio-filter) from the chloramine. However, in an ever escalating battle for market share, the makers of our dechlorinators have decided to keep adding extras we don't need and may in fact harm our finned freinds. While the addition of chems to "build up the slime coat" or "help with stress" seem like a great idea, they can also irratate the gills and cause excessive slime coat to build up there making it difficult to breath if used improperly. By itself, this is seldom an issue, but coupled with an already stressed fish due to an improper water change it can be a contributing factor.
When I do my water changes I first remove the water, add my ST and let it circulate, then slowly add my new water. After about 1/4-1/2 my water has been replaced I then add prime at 1/4 dose, just enough to take care of any ammonia released by the chloramine.
Not a big fan of amquel+, the original amquel was much better IMHO. While an OD might have added to the problem I highly suspect it was not the main source. You should check the water parmeters of the water you are adding as well as the tank water. I know my tap water can very from 7.8 to 8.6 PH. Others here may never have this issue, it all depends on your LWTP. However, the most important of all the parameters when doing water changes is temperature!
I know there are lot of fans of everyones favorite dechlor, but in my expeirance nothing beats good ol' ST. Sure you might get a slight ammonia level (which would hardly be detectable and easily handled by your bio-filter) from the chloramine. However, in an ever escalating battle for market share, the makers of our dechlorinators have decided to keep adding extras we don't need and may in fact harm our finned freinds. While the addition of chems to "build up the slime coat" or "help with stress" seem like a great idea, they can also irratate the gills and cause excessive slime coat to build up there making it difficult to breath if used improperly. By itself, this is seldom an issue, but coupled with an already stressed fish due to an improper water change it can be a contributing factor.
When I do my water changes I first remove the water, add my ST and let it circulate, then slowly add my new water. After about 1/4-1/2 my water has been replaced I then add prime at 1/4 dose, just enough to take care of any ammonia released by the chloramine.
