I got a couple of 20L buckets of beach sand a couple of weeks ago from a local beach which I've been washing out. I wasn't that keen on the browner look that beach sand gives, but caved to impatience and decided to use it. The added PH buffering I'll get will also be beneficial to my africans. For interests sake, I took a PH reading before adding the sand so just straight tap water, and it was around 7.2-7.4. I added the sand, gave it a couple of hours then took another reading and it was 8.8 or possibly higher! I took a photo of the two tests side by side which I'll try and load tomorrow, but if the PH is closer to 9 it's no good for fish right? How high is to high for malawis?