Thanks Jen

I did a waterchange when I got home from work and took more pics but photobucket are doing some site maintenance so have to wait to upload them.
I had to pull another 3 dead little guys out today and thought what am I doing wrong? I think it's a lack of aeration. I have 2 airpumps connected to a couple of sponge filters but as the temp's a steady 24, I needed to increase the oxygen. So I raced off to get another pump

and set up an airstone and now there's quite a bit of water agitation. I really want to try and hang on to the remaining 16 and see how they turn out...
The strangest thing is several (which doesn't auger well) have whitish growths around the gill area and this is the first sign that all isn't well. I don't know what it means but hopefully the additional air will help them. They've been quite sluggish

Ah well, only time will tell what will happen but at least they're in excellent heated, filtered and well aerated water now