fish are still dying

[Rocket Girl]

I have tried to change the pH before. It is damn near impossible and all you end up with at the end is an unpredictable pH that can swing.

No thanks.

What possible difference could squeezing a sponge make? It's not like you're going to squeeze out the bacteria.

 

[TankGirl]

During the cycle and shortly after a cycle completes you can indeed disrupt enough bacteria to stall your cycle by squeezing out the sponge. This goes against what many will tell you, but I have determined for myself that any kind of physical disturbance of surfaces in the tank during the cycle can kill off some bacteria, and "some" bacteria is all you have at that point. There is just not a lot of it early on so it is easy to lose enough to crash the tank. Later on there are tons of bacterial colonies everywhere, glass, gravel, decorations filter box, everywhere, that changing out the filter pads completely won't even cause a blip. I have learned to take the hands-off approach during a cycle.

I do wonder if "most LFS keep their tanks at 7" because in my city this is certainly not the case. They will tell you "we try to keep them around 7" but when you test their water yourself you get what I get out of the tap - 7.4 to 7.6. It is very wise to find this out for sure and definitely slowly acclimate the fish to your own water. I get my own little sample of tank water from the tank where the fish are coming from if I have doubts, and test it when I get home.

pH stability is dependent on alkalinity (buffering capacity) in the water so sometimes you are fighting a losing battle to try to alter your pH if you have a low KH, and since most farm-bred aquarium fish can do just fine in a wide range of pH levels it is generally better to leave pH alone. Just my two cents - there is an entire thread on pH here: http://www.aquariumadvice.com/viewtopic.php?t=11464