nilocg aquatics aquarium fertilizer | ferrum liquid iron 500ml bottle highly concentrated iron supplement for planted tanks nilocg aquatics iron is an immobile nutrient in plants meaning that it cannot be scavenged from older leaves. this makes it very important to have a constant supply of available iron. ferrum it a highly available form of ferrous chelated iron. other cheaper iron supplements use iron in the ferric form which makes it less available. dosing instructions are 1 pump per 10g 1-3x per week depending on the needs of your tank to maintain 0.1ppm iron.