2.5 gallon nano - help needed please
I've got a 2.5 gal AGA tank that's been set up since November '07. Here are the specs:
18W Coralife Mini
1/4 inch of potting soil (I don't know what brand, etc as I threw away the bag, and had been storing it in a tupperware cntr for about a year before I used it.) It's got some small pieces of bark in it, and I picked out most of the pearlite before adding to the tank.
1 inch of regular conga rock/aquarium gravel
Zoo Med 501 canister filter w/ lily pipes, bio rings & filter floss only.
DIY CO2, random trace/iron ferts.
Shou stone from ADA, said to be inert, but I never tested it.
Planted w/ HC and dwarf hairgrass.
Only inhabitants now are cherry shrimp. Moved the remaining 2 boraras micros (started w/ 6) to my 29 gal last month, as they hadn't thrived / gradually died every month or two in the 2.5 gal.
So here's the deal. My tap water is a fantastic 2 - 3 GH/KH. But my tank stays at around 9 KH & 11 GH. For the first 3 months I had zebra rock in the tank rather than shou stone, and when I realized my tank's hardness had gone through the roof, I did some testing of the zebra rocks sitting in tap water for a week and found moderate (6 GH), but not extreme buffering going on. So in February I pulled them all out and replaced them w/ the shou stone.
BUT, my KH/GH continues to stay around 9 & 11. After a 50% water change I can get them both down to around 7 or 8 but w/in 3 or 4 days they're back up again. I've contented myself lately to do just a quart WC at a time, a couple times a week, so as not to stress the shrimp too much. Still, they've never once bred in the entire 6 months (I've lost a few, replaced a few during that time as well).
You guys think there's still sediment from the zebra stone in the tank that's causing the hard water, or something else? In 3 months' worth of WCs, wouldn't you think I'd at least see some drop in hardness?? Would appreciate any suggestions you guys have. Thanks!