i need help now

[untamed]

Originally Posted by draco

i was told it is the most important with top up cause you are not taking anything out. where on a water change you are taking out so you can put the tap water back in. i dont know, but i have access to the RO water easily so i think that i will do my changes with it from now on. and leave it to cure for awhile.

Whoever told you that one is just plain incorrect.

Just to be clear...
Evaporative top up - use RO water
Water change - use SW mixed using RO water.

Just don't allow tap water to ever enter the system. Plain and simple.

My $.02: I do 10% water change weekly using SW that I mix and use immediately after mixing. It's not the best procedure, but it has never caused me any problems in 3 years. In fact, due to the new SW being cold, the tank temp drops by nearly 2 degrees C each time I do it. Bad...but no dramatic effect like you are experiencing.