I honestly don't think the phago will give you what you're looking for. If the RHF wolf doesn't work for you, I'd look into getting something else. If you already plan on upgrading to a 35, why not get it now and get something else for the 20? It shouldn't be that long before the wolf outgrows the 20. A 20 gallon really limits you. Have you looked into any fw or brackish puffers? I don't remember the max size, but I think a congo puffer may be fine for a while in your 20. They're not that active, but you have to sacrifice activity level if you want something that's not neon tetra size.