← Waterbox Cube 20 (AIO) · All nano protein skimmers
Best skimmers for the Waterbox Cube 20 (AIO)
Choose a skimmer whose manufacturer-rated volume meets or exceeds your tank volume multiplied by a safety margin: 1.2× for light bioloads, 1.5× for medium, and 2.0× for heavy. This compensates for manufacturer overclaiming and the tendency to overstock nano tanks. If you're using an in-sump or in-chamber skimmer, confirm it physically fits the rear chamber, which is often only about 3 inches front-to-back; hang-on-back skimmers sidestep that constraint.
The Waterbox Cube 20 holds 20 gallons in a 17.7 × 17.7 in footprint and ships without a light. Its manufacturer-published rear chamber is 7.9 in wide × 3.1 in deep × 15.7 in tall — the 7.9 in width is unusually generous for a 20-gallon AIO and fits most nano skimmers side by side, but the 3.1 in depth is still the constraining dimension for front-to-back clearance. The stock return pump delivers approximately 264 GPH.
K1-Nano Protein Skimmer $98.16
- rated to 30g, covers your 30g medium-bioload target (tank + margin)
- 3.2×2.75" footprint fits the 7.9×3.1" rear chamber
All skimmers compared
| Skimmer | Rated to | Mount | Price | Verdict |
| K1-Nano Protein Skimmer IceCap | 30 gal | in-chamber | $98.16 | Top pick |
| Comline DOC Skimmer 9001 Tunze | 37 gal | in-chamber | $149.99 | Recommended |
| AquaMaxx HOB-1 AquaMaxx | 75 gal | HOB | $189.99 | Recommended |
| Classic 100-HOB Skimmer Reef Octopus | 105 gal | HOB | $334.94 | Works, oversized |
| Bubble Magus QQ2 Bubble Magus | 26 gal | in-chamber | $99.99 | Undersized |
| Bubble Magus QQ1 Bubble Magus | 25 gal | HOB | $95.99 | Undersized |
| SkimMate Ghost Skimmer (Desktop) Innovative Marine | 20 gal | in-chamber | $149.99 | Undersized |
| Comline DOC Skimmer 9004 Tunze | 66.1 gal | in-chamber | $199.99 | Doesn't fit chamber |
| Classic 110-INT In-Sump Skimmer Reef Octopus | 130 gal | in-chamber | $326.85 | Doesn't fit chamber |
FAQ
Do I need a protein skimmer on a nano AIO?
It depends on your bioload. Lightly stocked tanks with frequent water changes can often skip a skimmer, but a heavily stocked nano benefits significantly from one. If you're running a heavy bioload, size up to a 2× safety margin on the manufacturer's rated volume.
Why apply a safety margin to the manufacturer's rated volume?
Skimmer manufacturers tend to rate their products under ideal, lightly stocked conditions. Nano tanks are also easy to overstock relative to their water volume. Multiplying the tank volume by 1.2 to 2.0 depending on bioload gives you a buffer against both factors.
My AIO rear chamber is only 3 inches deep — what are my options?
In-chamber skimmers must fit that footprint, and many don't. Measure the front-to-back and left-to-right dimensions of your chamber before buying. A hang-on-back skimmer avoids the fit problem entirely since it mounts on the tank's back wall instead of sitting inside the chamber.