We have a small 6 gallon tank we keep 3 guppies in (recently added one oto). We've had the tank a few years, after losing a couple bettas we thought we'd try guppies. We've not had a lot of luck. The first set we got from Petsmart, 2 died, we chalked it up to being Petsmart and found a local store. The 3rd guy actually just passed and we had him a year (our longest!) And seemed to have swim bladder issues? We had two other sets and they just don't last longer than 6 months (one jumped out of a tiny hole in the back, bad luck). But I test the parameters and the fish store guy told me it was OK we had 0 ammonia, nitrite, and nitrates. We keep a live plant in there. The only thing "off" is our pH is like 8.4. I added a catappa leave and it was 8.2. Someone mentioned a high level may be what our trouble is? Straight out of our well water tap it's 7.6. So how, or should, we even try to address it? Should we do more water changes (we do like once every 3 weeks). A couple weeks ago after my husband changed the water the fish seemed stressed and one died, but the other two bounced back (until this other died yesterday). I wonder if he changed too large amount of water...I think it should only be 25%? We're getting ready to call it quits because it shouldn't be this difficult! We have a 90 gallon my husband has kept for 20+ years and never had issues with...we have a parrot cichlid who actually refuses to die in there now! Keeping this smaller tank has proven to be much harder!