Would you repurpose this?

[cj in sac ca]

Here in Pensacola Craigslist has some food grade ones pretty cheap every couple weeks. I bought a 120 gallon rubber maid stock tank and set it up in my garage to use as a holding tank for when I do water changes. I have a few small live rocks in it I add water and salt a day or so before then add a pump to keep it circulating and then the next day or so do a water change on my 90 gallon local tank.

 

[Randy Holmes-Farley]

What about soaking it down with muriatic acid?

That may be helpful. In general, inorgnaic compounds (like copper ions) won't penetrate plastic to an extent that is a concern, so if the surfaces are cleaned off, it should be good to go.

Organic pesticides, mold inhibitors, or antimicrobials would be much more of a concern if it ever held them.