The Exo Terra 25 gallon tank is the Exo Terra All Glass Terrarium in its Large/Low configuration, measuring 36" x 18" x 12" (LxWxH). It holds approximately 27 actual gallons and is designed specifically for reptiles and amphibians, with features that distinguish it from a standard aquarium. If you're trying to figure out whether this is the right enclosure for your animal, what equipment you need, and how to set it up, this guide covers all of that.
Keep in mind that Exo Terra sells multiple large configurations, and the "25 gallon" designation varies somewhat by retailer. The most common candidate is the PT2611 (36"x18"x12") or the PT2612 (36"x18"x18" at approximately 40 gallons). Double-check the internal dimensions rather than the listed volume when buying.
What Makes the Exo Terra Terrarium Different from a Standard Aquarium
A standard fish tank is a rectangular glass box designed to hold water. An Exo Terra terrarium is engineered around the needs of terrestrial and semi-arboreal reptiles and amphibians. The differences matter when you're setting up an enclosure.
Front-Opening Hinged Doors
The most significant feature is the dual-hinged front doors. For aquatic tanks, access is from the top. For reptiles and amphibians that have a defensive startle response to overhead movement (a predator silhouette from above), front access is far less stressful. Feeding and maintenance happen at the animal's eye level, which also makes routine care much easier.
The doors have an escape-prevention lock and a mesh insert that can be used for ventilation or feeding without fully opening the doors.
Raised Bottom Frame
The Exo Terra terrarium has a raised bottom frame that allows you to run a heat cable under the enclosure for belly heat, or to fit an under-tank heater (UTH). This is a detail that fish tanks don't have, because aquatic setups heat the water directly.
Full-Screen Top
The top panel is a full-screen (usually removable aluminum mesh) that allows for UVB and heat lamp placement. The mesh also provides ventilation and humidity escape, which matters for arid-adapted species. For high-humidity setups (tropical frogs, crested geckos), you'll partially cover the screen to retain moisture.
Wire and Tube Management
The background has integrated holes at the top corners for routing heating cables, temperature probes, and misting system tubing. This is a practical detail that a converted fish tank simply doesn't offer.
What Animals Fit Comfortably in a 25 Gallon Exo Terra
The 36"x18"x12" dimensions make this an appropriate enclosure for:
- Leopard geckos (single adult): Floor space of 36"x18" exceeds the commonly cited minimum of 20"x10". A 25-gallon or 40-gallon breeder is the standard recommendation for one adult.
- Crested geckos (juveniles to young adults): The height (12") is marginal for adults, who need vertical space. The taller 40-gallon configuration (PT2612 at 36"x18"x18") is better for adult crested geckos.
- Blue-tongued skinks (juveniles): Adults need more floor space (4'+ enclosure), but this tank works for juveniles up to 8-10 inches.
- Small bearded dragons (juveniles under 10"): Adults need 4x2x2 feet minimum. This is a short-term setup only.
- Dart frogs (small groups): The bioactive vivarium community frequently uses this exact enclosure for dart frog groups, especially Dendrobates tinctorius and Ranitomeya species.
- Pacman frogs: One adult fits comfortably with appropriate substrate depth.
It is not appropriate as a primary enclosure for adult ball pythons (need wider floor space), adult chameleons (need taller, screen-sided caging), or any large monitor species.
Setting Up a 25 Gallon Exo Terra: What You'll Need
Substrate
Match substrate to the animal's natural habitat. For leopard geckos, a bioactive mix of organic topsoil and play sand (60/40) with a drainage layer works well. For dart frogs, ABG mix (a blend of orchid bark, sphagnum moss, coconut fiber, and charcoal) is the community standard. For a humid tropical species like a tree frog, Zoo Med Eco Earth or ReptiSoil holds moisture well.
Avoid calcium sand for any species. It compacts poorly, causes impaction when ingested, and doesn't support beneficial microorganism colonies.
Heating
The type of heating depends on the species. Most reptiles thermoregulate by moving between warm and cool zones, so you need a thermal gradient.
- Under-tank heater (UTH): Fits under the raised bottom frame. Use a thermostat (Inkbird IBS-TH2 or Herpstat 1) to regulate temperature. Never run a UTH without a thermostat.
- Basking bulb: For diurnal species that need a heat gradient and basking spot. A 40-75W incandescent in a dome reflector creates a basking surface temperature of 90-100°F for leopard geckos and blue-tongued skinks.
- Deep heat projector (DHP): The Arcadia Deep Heat Projector 50W is increasingly preferred for belly heat in leopard gecko setups because it penetrates substrate and more closely mimics radiated ground heat.
UVB Lighting
This depends on the species. Many keepers still maintain that leopard geckos don't need UVB, but the emerging science suggests they benefit from low UVI exposure (Arcadia 6% T5 HO or equivalent). Bearded dragons unquestionably need strong UVB. Dart frogs and nocturnal species have very low requirements.
For a general setup, the Arcadia T5 HO 6% UVB 22" tube fits the 36" length comfortably and is among the most reliable in the hobby.
See our Best Aquarium Equipment guide for more on lighting and heating equipment options that cross over between aquatic and terrarium setups.
Common Questions About the Exo Terra 25 Gallon
The biggest confusion with this enclosure is whether it can be used as an aquarium. The answer is no, at least not reliably. Exo Terra terrariums are not rated for water pressure. The silicone seams are designed for incidental humidity and moisture, not for holding 25 gallons of water. Filling one as an aquarium risks seam failure.
If you want a bioactive vivarium with a water feature or paludarium (part aquatic, part terrestrial), the Exo Terra can handle a small water section in one corner with a shallow reservoir, but it's not a substitute for a proper aquarium.
Also worth noting: the screen top is a heat escape point. In cool rooms, maintaining a basking spot above 95°F can require a significantly higher wattage bulb than expected. Covering part of the screen with a piece of cardboard or a thin foam sheet during cold months can help retain heat without buying a larger bulb.
Our Top Aquarium Equipment guide covers additional accessories and supplemental equipment relevant to naturalistic enclosures.
FAQ
Is the Exo Terra 25 gallon good for a bearded dragon?
For a juvenile under 10 inches, it works temporarily. Adult bearded dragons need a minimum 4'x2'x2' enclosure. If you buy this for a baby beardie, plan to upgrade within 6-12 months as the animal grows.
Can I use the Exo Terra as a fish tank?
No. The tank is not designed or rated for water pressure. The silicone used at the seams is not aquarium-grade. Using it as a water-filled aquarium risks leaks and potential failure.
What's the difference between the PT2611 and PT2612?
The PT2611 is the Large/Low configuration at 36"x18"x12" (approximately 27 gallons). The PT2612 is the Large/Tall configuration at 36"x18"x18" (approximately 40 gallons). The PT2612 is better for arboreal species that climb.
How do I maintain humidity in an Exo Terra for a tropical species?
Cover 50-70% of the screen top with glass, foam, or a custom lid insert to retain humidity. Add a large water dish, use a moisture-retaining substrate like coconut fiber, and consider a reptile fogger or automatic misting system (Mist King Starter System is the most reliable in the hobby) for species needing 80%+ humidity consistently.
Final Thoughts
The Exo Terra 25 gallon (PT2611) is a well-built enclosure that works very well for leopard geckos, dart frogs, and similar small-to-medium terrestrial or semi-arboreal species. Its front-opening doors, raised bottom frame, and wire management features make it genuinely more practical than a converted fish tank. The main limitations are height (low configuration limits arboreal setups) and the inability to use it as an actual aquarium. Match it to the right species, pair it with a thermostat for any heating element, and you'll get reliable performance for years.