I use pool filter sand in my 55 gallon tank with 8 GBR's that dig pits when they spawn, and 2 BN plecos that are all over the place, and I have never had a problem with it hurting the fish in any way. Loaches sould be fine but may prefer a finer grain substrate. The nice things about pfs are: it is CHEAP ( I spent $8 for a 40 or 50 lb bag and didn't even use all of it in my 55 gallon), it looks nice (in my opinion at least), and it is easy to clean compared to other substrates.
About the gas buildup problem... I am not sure how often you need to stir because I clean my tank about every week and a half or two weeks at the most, which should get rid of any gas that has been built up, and have never seen any gas that escaped in an area that wasn't planted. I have changed my live plants around many times and the only time that I ever see a buildup is when I move the aponogeton that is a bulb plant. My numerous swords, wisteria, anacharis, jungle vals, etc. never had any gas escape from under them when I moved them.