I'd recommend a big ATO reservoir & Innovative Marine builds about as nice of a one as there is.
It's glass with a slide out fill drawer, to help prevent spills. Also has a cable slot for your ATO pump & a float/level indicator.
The 15 gal. model is $149 list, but it's been on sale at least twice in recent memory (10 or 20% off?).
Here's a video for you with link to Marine Depot below that-
Keep your Innovative Marine All-In-One tank running crystal clear with the NuvoSkim DC Protein Skimmer! Finding a skimmer that will fit in the back chambers of an AIO aquarium can be challenging, but Innovative Marine's NuvoSkim DC has a small form factor and gives great results. The DC powered...
www.marinedepot.com