First question is, my lfs has some stock of seachem flourish that was
bought by previous management.. they don't know how old it is, so i'm
wondering if the stuff can go off? it seems unlikely but it does recommend
being stored in a fridge after opening..

It will probably be all right, if it hasn't been opened.

If you don't refrigerate it after opening, something starts to precipitate out
of it, making it cloudy at first, then sludgy. However, the Custom Sealife
people say it's still safe and effective to use. It's just ugly.

Anyway, every now and then there is this kind of 'burp' of
gas from beneath one clump of elodea, quite a big bubble maybe the size of
my thumb? it seems a bit early in the tanks life (2 weeks) to be getting
toxic gas production, so can anyone suggest what it could be??

If it's toxic gas, you should be able to tell by the smell. It will stink to
high heaven.

It could be oxygen. If plants are growing well, they can pearl under the
gravel, as well as from their leaves. But usually the bubbles aren't that big.
And, aside from the chain swords, you don't have the kind of rooted plants
that do this.

Do you have a UGF? If so, then it sounds like what happens when you don't have
enough gravel over it.


Leigh

http://www.fortunecity.com/lavender/halloween/881/