HAhaha! Think I spoke too soon! Had him in the epsom salts while I posted my last cry for help, went out and there was about a 3mm round ball of poop (is that extremely large or what? No wonder he couldn't get it out by himself!) and a couple of other little bits as well! So I put him in the plain fish water to rinse off a bit, then back into his tank to feed. Hope he continues pooping now!
Tikibirds - thanks for the suggestion
I've seen glass shrimp before - they're pretty cool. I'll look around and see what the most interesting ones I can find are... I'm guessing they're massive breeders though and I've heard they might be very messy, but I guess with cleaning the betta tank so often anyway it wouldn't be all that different!
Sakura8 - never heard of those snails, I'll look into that too! Thank god for the internet or all this research wouldn't be possible (or at least not as simple!)
snowtail - I got mine from the op shop in my town, but I've seen similar (lighted) ones for sale here (in Australia) in aquariums that sell the more expensive betta fish. You might be able to find them on ebay. I do like the ones like this: http://www.ebay.com.au/itm/Goldfish-...item3a6da4dda2
and this: http://www.ebay.com.au/itm/Fighting-...item27bd91ef7e
and I love this idea too: http://www.ebay.com.au/itm/NEW-WALL-...item2c619b239e
Thanks for everyone's help and advice
Let's hope my little boy stays well now! Thinking maybe his name should be Felix...? Or something else with an X in it... Hmm... *ponders*