Could you post a picture?
I can't solve your plant mystery other than to say that it was probably a hitchhiker of some kind. I just bought some assassin snails and was a little horrified to see the store tank they were in covered in duckweed. I made sure to keep them in a quarantine jar before adding them to my tank to make sure that I didn't add any duckweed to any of my tanks.The pleco was the last one I added and that was 4 months ago. I bought him because I was getting relentless hair algae that I would wash off the decor but it would grow right back. I'm not even sure what caused the hair algae. The snails were a month before the pleco.
If it were me, I'd get rid of it and replace it with a plant I chose myself. Live plants are really good for a tank and the fish love them. There are some really easy ones like guppy grass or anacharis.Ah thank you.. I am guilty of working too many hours and leaving their light on for too long more often than I know I should. I know I need to get an outlet timer but haven't made that happen yet.
The glow fish really seem to like the strange plant and hang out around and in it. Do you think it's safe to keep or should I take it out?
Me neither. I have HOB filters and I attach baffles made of plastic water bottles to disperse the outflow. I have to replace those periodically because algae grows directly where the water hits the baffling. I don't have much algae in my tank. But the worst of it is the lip where the water pours out of the HOB filter.Reducing the light will help with the cyanobacteria, but may not get rid of it. Nothing will really eat it so maybe just wipe/siphon out some here and there. There are chemicals you can use, but I've never bothered. Some people will say more water movement/agitation helps, but that hasn't been my experience. I've had it many times in many of my tanks. It just looks bad, but isn't dangerous to the tank.
It's not particularly bad. I'm fortunate enough that that's the worst I see of algae or cyanobacteria in any of my tanks. I have a lot of fast growing floating plants that outcompete most algae for nutrients and I limit the duration and/or intensity of the lighting in my tanks.Cyanobacteria may also be called blue green algae, but it is not an algae.
Flow, air, agitating the surface … won’t help with algae. If you’re having issues with algae close to the outlet of a HoB, maybe get some moss in that area if you like the look that is. Most moss will do well in/out of water in those situations.