Has anyone seen this product, currently for sale on ebay, before? http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1290897355 It's apparently a liquid that you dose the aquarium with over a 2 day period and it's good for 2 weeks. Any idea how this might work? It's not economical since, for three bottles which are presumably good for 6 weeks, it costs $15 + shipping. Roxanne Bittman