Yes, the onyx sand will make the ph rise slightly. When the CO2 in my tank was finished and I hadn't realized it, the ph would go to 7.2ish. When the CO2 is ok, its around 6.8-7.0ish.
Here is a picture from when my yo-yo loaches were babies. They are on the sand.
Here is a picture from when my yo-yo loaches were babies. They are on the sand.
