May I suggest that water conditioners won't need their own category, but perhaps replace that with Misc or Other?
Also, what is the rule on trades? Can anything be used for trades to obtain aquatics? (Ie. games, mom's home baked cookies) or just Aquatic related trades? I don't think I've ever seen an aquatics forum allow non aquatics things to obtain trades, but that could be a unique opening for us? Just brainstorming here. Feel free to agree/disagree.