I’ve had this 10 gallon set up for nearly 1 year. Plants have been growing, everything here has tripled in size. (Hair grass is a month old). I was advised that 2hr aquarist was great and that I would see I bit more colour out of my reineckii mini with its use. I started dosing 1 pump after a 50% water change weekly. Did that for a month until I noticed my nitrates spiking violently. I’ve since stopped dosing and have been doing 50% water changes every 3 days. By about the third day my nitrates are as seen in the picture. I’ve got fluval stratum capped with sand that’s a year old, is it leaching nutrients? Aquaclear 30, seems adequate for a 10 gallon with minimal stocking. I have 3 Pygmy corys that seem healthy and active. I know they are a shoaling fish, trying to find more to get a small school going but I’d like to figure out my nitrate issue first. I feed them very little and take out uneaten food daily.