Question about cleaning tank.

[WildType]

Hello everyone, I've had my two axolotls for 5 months now and I was wondering about the slimy gunk that forms underneath the filters and my aquarium hood is and how can I prevent it? Is it leftover pellets? Also theres a white mold type of substance that forms on the hood and filters as well...I would like to know the cause for this?

 

[Beate88]

Think you should clean that out. Could just be some algea, but the thing you describe as mold underneath the lid would be best to remove I think. What kind of filter do you have?