Funnily enough i used to work in a fish warehouse when I was a schoolboy.
If I were you just go over there , clean the filter out using the existing water, rake the gravel up a bit and get any shit out that you can , do a partial water change (10/20pc is fine but make sure the water isn't too cold) then lob one of those feeder things in and you should be ok for a while, as long as you keep doing the partial water changes every 14 days.
Moving the fish should be an absolute last resort.
Funnily enough i used to work in a fish warehouse when I was a schoolboy.
If I were you just go over there , clean the filter out using the existing water, rake the gravel up a bit and get any shit out that you can , do a partial water change (10/20pc is fine but make sure the water isn't too cold) then lob one of those feeder things in and you should be ok for a while, as long as you keep doing the partial water changes every 14 days.
Moving the fish should be an absolute last resort.
It's a kind thing you are doing.