IDK about that ALGONE stuff, just because most ppl here try to encourage ppl to not add things like that unless neccessary. And besides that, once you take the teabag out, then the trates will likely go back up.
20 trates isn't that high I don't think. Maybe you want to add a refugium like cahuama suggested. You don't even need a HOB though cause you got a sump. Just add some Chaeto, pods and lights, and you should have 0 trates.
IDK if you have any filters, but if you do, maybe you sould clean them out.
As for the feeding, I agree you should feed frozen. I feed brine w/ spirulina (Brine is not the best food though), Mysis, and marine cuisise. Just take a very small chunk since you only have 1 fish, put it in a cup w/ a littl ebit of you tank water, and mix it up a bit.
When I feed, whether it be frozen or dry, I feed a little bit, let my fish eat it, then feed a little bit more, then let them eat it etc.
That way, not much goes to waste. If you thrown in 10 pellets at once, how fast can you fish eat? It's going to fall to the sandbed. If you throw 1-2 in, he'll eat them, then you throw in 2 more...
But yeah, go with frozen. I use the same method of feeding for frozen also. Pour a little bit of the tank water mixed w/ food at at time. Also, frozen doesn't sink to the bottom qUITE AS FAST.