I have no experience with dosing ferts. The plants I have all grew very well in an iron and mineral rich soil base which I have recently removed. The tank is bare bottomed now with the plants tied to wood. The water is ok for GH and KH, ~10 ppm nitrate and the lighting is low medium. The plants seem undaunted so far but I doubt it will last. The fish (goldfish) produce a lot of waste and I change a lot of water but I suspect I will have to add something to keep the plants thriving. I don't know where to start beyond that I know that I have enough nitrogen from the fish waste. I imagine the plants will need iron but don't know about potassium or phosphate. I don't really want to buy iron, P and K test kits right now and am very tempted to just start adding flourish and hope it covers all the bases. Is this likely to work or should I do something else?