Best 40-Gallon Breeder Tank (or a 55)
2 minute read · Updated November 10, 2026
Edited by Ivan F.
Quick answer
A 40-gallon breeder is wide and shallow, which gives fish floor and surface and makes it easy to reach the bottom. A 55 is longer and taller but narrower. Either weighs several hundred pounds filled, so choose the stand and the spot in your home before you choose the tank.
Why go this big
A welfare charity says larger volumes hold more stable temperatures and water conditions, and a trade association says larger aquariums contain more water, so they will be more stable. At this size you have room for larger schools and for fish that need territory. In liters, by our arithmetic, 40 gallons is about 151 liters and 55 about 208.
Two common shapes
| 40 breeder | 55 | |
|---|---|---|
| Length × width | About 36 × 18 inches | About 48 × 12.75 inches |
| Height | About 17 inches | 21 inches |
| Filled weight | 458 lb | 625 lb |
| Suits | Bottom dwellers, territories, planted tanks | Active swimmers that need length |
Sizes and weights are from one maker’s chart, rounded. Which shape suits which fish is our advice.
How to choose
- Floor and surface. A welfare charity says wide tanks are better than tall ones, because surface area is where oxygen enters. The 40 breeder’s depth front to back gives more surface than its gallons suggest.
- Length for swimmers. The 55 is a foot longer, which suits fast schooling fish.
- Height for tall fish. One retailer says tall-bodied fish need vertical height, and the 55 is the taller of the two.
- Reach. A shallower tank is easier to plant and clean by hand. This is our advice, not a measured finding.
The stand and the floor come first
- Use a real stand. A veterinary manual says the floor and stand must be strong, level and stable, and the maker says a suitably designed stand is essential.
- Pick the spot. A trade association advises a place out of direct sunlight and away from heat and draughts.
- Check the floor. Several hundred pounds on four small feet is a real load. Put the tank near a load-bearing wall, and ask a builder if you are unsure.
- Plan for water changes. Moving buckets for a large tank takes time, so a spot near a sink or a hose run helps.
Bare tank or kit?
At this size kits are less common, and a bare tank with your own filter and heater is the usual route. If you buy a kit, check whether the heater is adjustable and big enough, and whether a stand is included. Browse fish that suit a 40-gallon tank to plan the stocking, and cycle the tank first.
Options that fit
Chosen against the criteria above. Nobody at AquariaWiki has used or tested these products. The specifications are the makers' own statements, so these are the strongest fits on the facts we could record, not a hands-on verdict.
Picks for the US
Aqueon Standard Glass Aquarium 40 Breeder US
Wide and shallow, with the most floor and surface of these picks, which suits bottom dwellers, territories and planted tanks. It is a bare tank, so add a lid, a filter and a heater, and a stand built for its weight.
The manufacturer states: Size 40 Breeder. 36.25 x 18.25 x 17 inches. 458 lb filled by the maker's size chart, which says filled weights vary with substrate and decor. Place it on a stand able to bear the filled weight. 5-year warranty.
Aqueon Standard Glass Aquarium 55 Gallon US
Longer and taller but narrower, for active schooling fish that need length, and for taller fish. It is the heavier of the two, so check your floor and stand first. It is a bare tank, so add a lid, a filter and a heater.
The manufacturer states: Size 55. 48.25 x 12.75 x 21 inches. 625 lb filled by the maker's size chart, which says filled weights vary with substrate and decor. Place it on a stand able to bear the filled weight. 5-year warranty.
Picks for Spain
Eheim clearTank 200 Spain
Deep front to back and fairly shallow, close in shape to a breeder tank. It is a bare tank of optical glass, so add a lid, a filter and a heater, and a stand built for its weight.
The manufacturer states: 200 liters. 90 cm wide, 50 cm deep and 45 cm tall. 10 mm optical glass. 3-year warranty.
Eheim clearTank 175 Spain
Shorter than the tank above and almost as deep front to back as it is tall, for a smaller space. It is a bare tank of optical glass, so add a lid, a filter and a heater, and a stand built for its weight.
The manufacturer states: 175 liters. 71 cm wide, 51 cm deep and 50 cm tall. 8 mm optical glass. 3-year warranty.
Frequently asked questions
Is a 40 breeder or a 55 better?
It depends on your fish. One maker's chart lists the 40 breeder at about 36 by 18 inches and the 55 at about 48 by 12.75 inches. The 40 breeder gives more depth front to back. The 55 gives more length for active swimmers.
How heavy is a 55-gallon tank when full?
One maker's chart lists its 55-gallon at 625 lb filled, and its 40 breeder at 458. A veterinary manual says the floor and stand must be strong, level and stable.
Can I put a 55-gallon tank on a regular table?
We would not. One maker says a suitably designed aquarium stand is essential, and the weight is far beyond most furniture. Use a stand sold for that tank size.
What else do I need for a large tank?
A filter and heater sized for the volume, a lid, a water conditioner, a test kit, substrate and a thermometer. A larger heater, or two smaller ones, is common at this size.