its on a mr aqua mini-L equivalent. 18" width, so the light is a perfect fit. as mentioned above, its still not powerful enough to be called a med light fixture. tank has no co2 or ferts, and has a SMS substrate. its basically a cpo tank but i want it to grow plants for aesthetic reasons. all my invert tanks are fully planted so i was hoping this would be a viable alternative to the finnex fixtures which are great, but cant grow red plants at all (not dissing finnex, i have a dozen of their fixtures and really like them). i also have a 24" mr aqua tester tank, with co2 and AS with a ray2 + monsteray combo and that is working out great. red plants are back to full red (rotala butterfly) and even marginally red plants (hygro pint.) are really red/magenta. its not just the light either, when i take it out it is really growing red. finnex should just combine the RGB leds into a ray2 and they'll sell a ton. if you can afford 2 fixtures, IMO go with a ray2/monsteray combo. youll get med/high light and the ability to grow red plants easily and pretty much anything else (tank also has erios and they are growing fine).