Not sure where to go for info, but hoping someone here might have some
advice...

Yesterday, we had a little fish tank episode... Our 5 year old put one of
those growing dinosaur toys in the fish tank (those things that you put in
water and they grow to something like 500x their original size)
I noticed a few of the fish weren't looking so hot... This tank in question
is 82 gallons, and it had a variety of fish in it and for so long, it's been
fine with what we've had in there... Some giant danios (1.5" or so long), a
Jack dempsey (about 4" long), pleco (about 5" long), rainbow shark (about 4"
long), and a handful of comet goldfish (ranging in size from about 1.5"-3")
All these fish have been fine together, never a problem, as they've all been
in this same community tank for well over a year now.
Some danios went belly up before I even realized this growing dinosaur was
in the tank. All the goldfish went belly up, or nearly belly up, and
eventually died. The rainbow shark was doing a crazy spinning manouver, and
the danios that were surviving at the time were kind of just swimming right
at the very, very top of the tank (they're normally schooling a few inches
below the water level, rather than right at water level, and they go back
and forth like crazy, now they were just kind of clumping together in the
corner)

The JD seemed to be doing fine, as was the pleco. I grabbed them out of the
tank, as well as whatever danios were still alive as well as the shark. I
put the surviving fish in a tiny 10 gallon tank that had some fancy
goldfish, corys and a pleco in it, as that was basically all I could do.
That 10gal was already far too crowded, yet the fish were doing fine, and I
had nowhere else to put the fish from the 82gal into. Now, in this tiny
10gal tank, there's a 4" black moor, 3" oranda, 4" comet, 1.5" comet, 4
small corys, the 5" pleco, a 2.5" pleco and I think about 3 of the giant
danios, along with the JD.

These poor fish are just going nuts being this crowded, although they seem
to be doing fine. Surprisingly, the jack dempsy is not eating the other
fish, nor does there seem to be any real issues at this point, other than
the fish being all crammed in a small tank. I need to get this bigger fish
tank done ASAP, but how on earth would I do this the best way possible? I
do think this growing dinosaur contaminated the water - I assume a full and
complete water change is necessary. I'll take out all the slate, as I had
to move rocks and stuff around to catch the dempsey and the pleco, but
should I take out all the gravel as well? I'm kind of wanting and needing
to move this fish tank over a few feet to make room for something else, but
there's NO way I could move this tank myself with water, gravel and rocks in
it, so would it be best to empty it out completely and totally and move it
while I'm going through this trouble anyways? Should I clean the tank glass
and start fresh or if the water has gone sour, would the tank still be
alright? What about the slate rocks? Gravel? Could any algae be
contaminated as well, making it a problem for something like the pleco?

Kind of ran into a mess, but maybe someone has some kind of advice?

TIA!

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