Disclosure: Coral Compass may earn a commission when you buy through links on this page, at no extra cost to you. Retailer links are marked as sponsored. This doesn't change what we recommend, and we haven't received free products from the brands listed. Full disclosure.
How to choose
All-in-one tanks hide filtration in a rear chamber, so there's no sump to plumb. That makes them the most common way into reefing. Check what's actually included (light, return pump, skimmer, ATO), because the true starting cost varies widely. Bigger water volume is more forgiving, so 20 gallons is a popular starting size.
- Budget for the light, heater, ATO, test kits, salt and rock if they aren't included.
- Cycle the tank fully before adding animals.
- Add an ATO early. Small tanks swing in salinity fast.
For the science behind it, read our Nitrogen cycle guide.
How we review: we paraphrase what owners report in retailer reviews and forum threads, plus picks and test results from BRStv, Reef2Reef discussions and published reef chemists. We only show a rating when we verified it at the source, with the date we checked. We don't invent scores or quotes. Prices and stock change, so check the retailer.
Well-regarded picks
Innovative Marine 20 NUVO Fusion AIO Long
20-gal AIO (tank only)
- What reviews say: strengths
- The few BRS reviewers praise build quality for the price, roomy rear chambers and dual returns.
- Weaknesses
- Light, return pump and other equipment are sold separately. BRS shows only three reviews.
- Who it's for
- Beginners who want a well-made tank and to pick their own gear.
- Expert consensus
- Innovative Marine NUVO Fusion tanks took the top two spots in BRS's 2024 best-selling aquariums list.
Where to buy:
Innovative Marine 20 NUVO Fusion PRO 2 with APS Stand
20-gal AIO + stand
- What reviews say: strengths
- It adds a matching stand and upgraded filtration chambers to the NUVO platform.
- Weaknesses
- It costs more than the tank-only version, and BRS shows no customer reviews yet.
- Who it's for
- Buyers who want the tank and stand to match.
- Expert consensus
- It's on the same NUVO Fusion platform that led BRS's 2024 aquarium best sellers.
Where to buy:
Red Sea MAX NANO G2 Cube (20 gal)
Complete AIO system
- What reviews say: strengths
- Per BRS's listing, it comes with a ReefLED G2 60 light, return pump, skimmer and gravity-fed ATO, so it's close to complete out of the box.
- Weaknesses
- It costs more upfront, and BRS shows no customer reviews for the G2 cube yet.
- Who it's for
- Beginners who want one box with matched equipment.
- Expert consensus
- We found no independent long-term test of the G2. Its included equipment is what sets it apart from tank-only AIOs.
No independent expert source verified. Summary based on retailer and manufacturer information.
Where to buy:
Spot an error or a product we should add? Specs and availability change often, so always check the manufacturer's current listing.