Mushroom growing in reservoir?

Im doing a ucdwc system and after each round i open up the system and clean every thing. This time i notice mushroom (large one) growing under lid and upper wall of the reservoir? is that a good or bad thing? have anyone experience this before? Thank for you view!

The mushroom might not be the end of the world but it certainly means that you have some sort of contamination problem, which could become a bigger issue.

i use benefit tea and add every 3 day. what should i do?

I don't know much about hydroponics but your best bet is probably just giving your res a good wipe down with bleach. Follow that by cleaning everything else in your grow space. If you do a thorough cleaning and get mushrooms again then maybe you have an air contamination problem elsewhere and the ventilation system is bringing it into your grow area. It's also possible that you somehow got some mushroom spores on your shirt and then walked into your room later that day, opened the res and a spore or 2 happened to fall in.