You always need to test when you dose anything. How are you going to know if you are adding too much or too little? Especially with the small water volume of a 29gal biocube. Iodine breaks down into iodate and iodide in the aquarium and different tanks metabolize it at different rates. Iodate can build up over time and you could damage your livestock. If your not going to buy the kit and test for iodine, you are taking an unnecessary risk.