Whatever you use better be disposable, if resin comes out, it is staying in the container unless you have a professional level degreaser.
If you have a health store, go check if they sell Rooibos Tea, might be called Red bush, but the real South African thing will say Rooibos.
You can just drop the teabags straight into the tank. You can remove them after a few hours when they are done leaching. Say you needed to use 4 on a tank. when you have to do water changes, if you change 25%, just add 1 bag again, 50% 2 bags, and so on. Makes it easy to maintain stable parameters. It is also very healthy.
Cape Town, South Africa.
Hi. I'm back.