I am currently forming a community tank. Anyway, I have been wanting put my guppies in with them, however my dilemma is that I have been keeping the water hardness in this tank at 6dH, is this too soft for guppies?
I wouldn't call your water "soft" compared to where I've lived, but I haven't kept guppies in it either. I "think" they'd be fine like Joel (FF) said. I'd say go for them!
It's MUCH easier to keep fish in your tap water parameters than to try & hit the "perfect" parameters. Really, my husband is a chemist & when, many years ago, we would read the "ideal, wild fish" pH or hardness, he could get it there, lol. Needless to say, our early fish suffered for the roller coaster ride we put them through. Don't do it!! Either guppies will be fine (likely) or you should find fish that can live in your water.
Heh, yeah. One time I had a super busy month, and didn't due any water changes in my guppy tank. I paid for that, they all had ammonia poisoning and I lost five fish. I made sure to always moniter the tank very carefully after that, and haven't had problems since.
Unless there was something else going on that you missed (an unrelated couple of fish death or something), the lack of water changes shouldn't cause ammonia to increase. That should only allow the organics and nitrates to creep up. If that (long time without water changes) happens, I'd do a number of smaller water changes to get parameters back to normal. It's probably overly paranoid, but I'd have concerns of Old Tank Syndrome, which I've had, and didn't know until many years later.
Guppies and Endlers are incredibly tolerant of water parameters, as long as ammonia and nitrite are not elevated.
I've kept Endlers in water ranging from incredibly hard (700ppm tds, 8.3 Ph) to quite soft (100tds, 7.0 PH) with no problems.