"change some of the water a little at a time"
My source water (tap) has about the same pH as the tank
"Using chemicals pH down is dangerous to your fish."
I quit trying three days ago. All fish are doing well.
"going to have to use RO water."
RO water?
"I am curious about the kH being 300 and the gH 0?? correct?"
That's the source water, yes. My tank's GH is closer to 50 because I put in maybe a liter of water from our old tank, which had a GH of around 100-150. I don't know why it's so alkaline, or if my test is just being weird/inaccurate. It's the same every time I test, though, so if something's wrong with it, it's a consistant mistake.
"I'm really surprised that the neons lived in the previous tank"
You and me both! But all four are swimming around and looking healthy at the moment.
"I'm curious - Are you using crushed coral gravel on the bottom."
I'm pretty sure not. I have biggish brown and white gravel. The white gravel smelled a little funny when I washed it, but our bathtub smells funny anyways and that's about the only comment I can make about any of it.
The tank has been running for about 72 hours now, and all seven fish are doing well. The neons are 'breathing' a little heavily - I wouldn't quite call it gasping, but I don't have a better word. They're schooling as normal and don't sit in the bottom or swim any differently than they did before (no crooked fish, yay!). All fins are unclamped, and the danios are content chasing each other around the rock they've got. So far so good! Ammonia isn't too high yet (between .25 and .5), and nitrites and nitrates are still low for an uncycled tank (Nitrite ~.5, Nitrate ~30 -- our old tank's nitrate level was constantly around 100ppm, so I consider that a small improvement?)
I've got a photo of the tank
HERE (It's kinda big). I think one of the danios is hiding behind the rock in that one.
~Edit
Snagged a quick picture while they weren't paying attention to me. Ha.
One of the danios snuck out of the frame again. He's in there, I swear, lol.
LINK
Looks like I need to wipe a couple of water spots off. Must have happened when I filled the tank.