Filters

[Dross]

Hello, so my project with the 3 litre tank isnt going well. anywho so, I've seen Ocean view sea monkey tanks, that are clean as a whistle. What would be best to keep the water "filtered" I understand that the "aqualeash" think if for sale here. I have one from a past sea-monkey tank, The deal Is how do people keep the water soooo clean and pretty? I mean. My sea-monkey/sea-dragon/cocoa snails/bubbles tank looks green and smells horrible. anybody have any ideas?
Im still working on the 3 litre but im going to make sure i know what im doing first.

Thanks for help or offers