Tank advice?

Hi all,

(waves at those I know from the goldfish group)

I have two tanks, a 30 gall with one 4" (2" of which is tail!) fantail
goldfish. It's healthy, still not cycled but I'm working on that with
Stability and hope that it'll get there. Sooner or later.

The second is a 10 gal that had started as the goldfish tank (long
story, not important now) but which is now a properly cycled (I test
regularly, it's good.) tank.

I made a mistake however and bought the first set of fish from a LFS
that I'm beginning to really distrust as far as their fish go. All the
fish I've lost so far have been from there and while some of the
losses were due to New Tank Syndrome, not all were.

It currently has two sunset platys who appear healthy although there
was a brief case of ich that I treated and which went away properly as
far as I can tell. I'm also almost certain the ich got in from the
first set, not this, but not absolutely. (FWIW, the LFS where I got
the platies and which I visited not long after showed no signs of
troubles with the tank.)

In any case, I plan on waiting at least two to three weeks before
getting any more tropicals to make certain the two left aren't sick.
Before I do, could I get some advice on about how many fish of what
size would be acceptable for a 10 gallon with two sunset platies in it
already? I like danios, platys, tetras (neon, but I know they can be
fragile), mollies and guppies. No great fondess for big or oddly
shaped fish.

Also, I'm currently doing the water exchange at about two weeks for a
25% change. I get a lot of the brown algae on the substrate, though,
so I'm considering making the change once a week. About how much of a
change would be reasonable under those circumstances?

Thanks in advance!

Deb