Hi UKAPS . Everything is going well with my planted shrimp tank, and I'm slowly winning against the staghorn algae that was running riot before I started to add CO2. But I've noticed what I think may be an iron deficiency in my hygro. It's only on some of the leaves near the light, and it also looks red too. My nitrate level is 15-20ppm and I'm dosing KNO3 so I've kinda ruled out nitrogen deficiency, and I'm thinking it may just be a little red because it's so close to the light. It's the glass-like appearance that I don't like. Here's a pic: So I bought some FeSO4 from fluid sensor, and added 2.5G to a bottle of 500ml RO water, and have been dosing 2-3 times a week to boost iron by 0.1ppm each time, I already dose the fluidsensor trace mix once a week at water changes (20g to 250ml of RO water then 10ml), so I've been assuming that combined with that I should have enough iron. Still got the same signs though, so I'm about to up dosing, buuuut... ...I'm really not too sure about the appearance of it in the bottle though, and when I leave it for a day it seems to settle on the bottom. Is there something else I should add to the solution? I tried some potassium sorbate in another bottle and it did the same thing, and I keep it in the dark when I'm not using just in case that has anything to do with it. Here's another pic: Maybe I should just put some rusty iron nails in the substrate, but I already have this powder, and I don't know how much my shrimp would like that . Does the solution look OK? Is this actually an iron deficiency.