If you read my previous post then you would know that I didn't mention anything about your hornwort.
Nails are not always the preferred way to maintain iron levels in an aquarium, but I have done it, and with good results. As for rust, obviously you should not leave them in the tank for more than a month.
Of course, a high quality plant nutrient solution is the best, I recommend Flourish.
Last edited by Scrambles; 02-05-2011 at 05:01 PM.