I started my 20 gallon (ca. 76 liters) nano tank in March 2020. My goal for this aquarium is ULM and a clown harem tank. Right now I have 3 clownfish and plan to add more soon and real anemone when tank is more stable. I have never done a water change and keep it topped off with an ATO and 5 gallon (ca. 19 liters) bucket reservoir (with RO water). ATO is very important to me because it keeps things ULM and keeps salinity (1.024) from swinging up and down. I ordered an AIO for my 20 gallon off Amazon and that's where I hide all my hardware (filter pads, bio balls, heater, skimmer, pumps, ATO). I love the idea of a refugium, so I bought a hang on breeder box and a grow light. I added Chaeto about 20 days ago and it has been slowly dying. I have tried about 3 different solutions and it turns out there wasn't enough phosphates. Right now my Nitrates=10 Phosphates=0. I do have a protein skimmer which makes no water changes much more doable. I also have the main display light only at 5% for about 3 hours, so I don't promote any unnecessary algae growth while it goes through the ups and downs of the tank. My goal is ULM and the only thing I do right now is fill the ATO reservoir once a week. I fit this all in the bookshelf I made for my desk (about an 18"x43" space).