fwiw, I would not add iodine for zoo or gsp growth unless the zoo and gsp growth was noticable not happening like it should. Your tank is far too young in my opinion to determine that sort of thing out yet. personaly, I'd advise that you stop adding the iodine for that reason. zoo's and gsp tend to be fairly hardy and will grow fine as long as your current and lighting are good. If you notice after another 6 months that they are not doing well at all, I'd look towards other problems being present than an iodine deficiency. Also, as far as chemicals like that go, if you do not have a test kit for iodine, I would not advise you add any. Same goes for all other supplements, if you aren't testing for them, do not add them. some things we do not test for so for adding filter feeding supplements, obviously we do not have a "chromoplex" test kit or anything, but for all water parameters, like Alk, Ca, Iodine, Magnesium, ect. ect. ect. Test for them if you plan to add the supplements.
