Miracle Mud..to try or not got go there?

[JPotter]

Oh dear..bought fish from LFS who knew it was a tiny tank!! I have 2x 30 gal and a 120 so may end up moving them if unhappy.
What fish do others put in a 10 gal?

Also I had read somewhwere of a method of large volume water changes to reduce nitrates...I think the initial change was huge followed by several 30-40% changes. I can't locate where I read this. Does this method have a "name", is there a reference site, is it feasible or another wrong direction like the cardinals and toby