It's kind of hard to tell for sure in the pics, but I think that might be black beard algae. That stuff is a pain in the neck to be rid of, but it's usually caused by an imbalance of ferts plus too much light relative to CO2 levels.
Try increasing your CO2 or gas exchange if not using CO2 and/or reducing photoperiod. Beard algae can synthesize carbon from the water column using minerals in the water that are unavailable to plants, but it can't do this without light, so cutting the photoperiod will slow it down. Making sure plants have access to sufficient CO2 helps them outcompete the algae for other nutrients.
A big water change to reset the nutrients in the tank will also help. They sometimes result when there is a surplus buildup of unused iron in a planted tank caused by plants not being able to metabolize it (which can also happen when there is excess phosphate, which is antagonistic to iron absorption, or too little potassium, which has a synthetic relationship with iron). A good water column reset will help balance that better if that is your cause.
Make sure to clean your filter sponge by squeezing out any gunk in dechlorinated water to remove excess spores and accumulated organic compounds that might cause a resurgence.
1 - 2 of 2 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.