Who Gives A Fish Forums

I've been dosing iron for over two years now, and after adding potassium, I started noticing issues with certain fish. Have you guys experienced anything similar? For me, it's been the Angelfish, Roseline barbs, and even some of my larger Bleeding Heart Tetras that seemed to be affected. These fish were healthy and thriving for over a year, but then they started to decline. I've had other fish die on me too, but those ones came in with internal parasites, so I'm not counting those. It's just these three species that seem particularly sensitive to iron.

Anyone else notice their fish struggling in a constantly fertilized aquarium?

I've had a different experience with aquarium plant fertilisers, having used them in both marine and freshwater tanks without any fish losses. My go-to is Sera Florena, a liquid iron-based fertiliser, and I make sure to keep the iron level below 1mg/l (1ppm) to avoid harming my fish.

It's crucial to do a substantial water change before re-dosing with plant fertiliser, as this helps remove any unused fertiliser and minimises the risk of poisoning the fish or overdosing on a particular ingredient.