A 20 gallon long aquarium measures 30 inches wide by 12 inches deep, which means you need a hood specifically sized for that footprint. Standard 20 gallon tall hoods (24 inches wide) do not fit. Most aquarium hood manufacturers offer the 30-inch size explicitly labeled for the 20 gallon long tank, though you need to confirm dimensions carefully because the labeling is not always consistent across brands.
Beyond sizing, a good hood keeps fish in the tank, reduces evaporation, and houses your light fixture. This guide covers the types of hoods available for 20 gallon longs, what features matter, and which specific models work well for different setups.
Why the 20 Gallon Long Needs Specific Sizing
The 20 gallon long is one of the most popular tank sizes in the hobby, particularly for fish that need more horizontal swimming space than height. Bottom-dwelling fish like corydoras catfish, loaches, and killifish all thrive in low, wide tanks. The problem is that the long footprint (30 x 12 inches) falls between the more common 24-inch and 36-inch hood sizes.
A 20 gallon high is 24 inches wide. A 29 gallon is 30 inches wide. Hoods made for the 20 gallon long are often interchangeable with 29 gallon hoods because they share the same footprint width. If you're shopping and can't find a hood explicitly labeled "20 gallon long," search for "29 gallon hood" as well.
Never try to use two 15-inch hoods side by side. The gap between them lets fish jump and increases evaporation, defeating the purpose of having a hood.
Hinged Glass Canopy vs. Full Plastic Hood
These are the two main categories, and they work quite differently.
Hinged Glass Canopies
Glass canopies are two-piece tempered glass panels that sit on a plastic frame resting on the tank's rim. A standard 20 gallon long glass canopy splits into a rear fixed panel and a hinged front panel, with a cutout in the back for cords and equipment.
The advantages are significant: glass doesn't discolor over time, it transmits more light than plastic, and it's easy to clean. Drip-off condensation also runs back into the tank instead of onto the stand.
The Aqueon Versa-Top 30-inch glass canopy is the most common choice for the 20 gallon long. It runs around $25-35 and fits the 30 x 12 inch opening. It comes in two panels with a plastic trim piece that can be notched to accommodate different equipment placements.
The limitation is that glass canopies don't include a light. You'll need a separate fixture, which also gives you more control over lighting type and intensity.
Full Plastic Hoods with Built-In Lights
Plastic hoods are one-piece covers that include a light housing built into the lid. They're the classic "kit tank" look and come with most beginner aquarium packages.
The Aqueon Deluxe LED Hood is the standard example here. It includes a built-in LED strip and a hinged front panel for feeding. At $35-50 for the 30-inch version, it's affordable and gets the job done for basic community fish setups.
The limitations are also notable. Plastic yellows over time from UV exposure. The integrated lights are usually low-intensity LEDs suitable for low-light plants at best. And when the light eventually burns out, replacing just the light component can be complicated.
Lighting Integration: What Options Do You Have?
If you go with a glass canopy, you pick your own light, which opens up a lot better options.
LED Strip Lights for Low-Light Plants
For a 20 gallon long with fish and low-light plants (anubias, java fern, hornwort), a basic LED strip like the Nicrew ClassicLED Plus or the Fluval AquaSky 2.0 works well. The Nicrew 30-inch version runs about $30 and provides adequate light for plants that don't demand high intensity. The Fluval AquaSky connects via Bluetooth to a smartphone app for scheduling and dimming, at around $50-60.
These sit on top of the glass canopy using built-in legs or clip onto the rim.
LED Lights for Planted Tanks
For a proper planted 20 long with demanding plants like carpeting species (Monte Carlo, dwarf baby tears) or stem plants needing medium-high light, you want more power. The Finnex Planted+ 24/7 HLC at 30 inches runs about $90 and provides 24-hour light cycles that mimic natural daylight. The Fluval Plant 3.0 at 24 inches won't span the full width of a 20 long, so the 36-inch version is the closest standard size, which slightly overhangs but works.
For more options across sizes and tank types, see the Best Aquarium Equipment guide.
Feeding Doors and Equipment Access
Most hoods, whether glass or plastic, include some form of opening for feeding and equipment access.
Glass canopies typically use a lift-and-tilt front panel. Plastic hoods usually have a small hinged door in the front. Both work but have quirks: glass panel hinges can break if not supported properly, and small plastic feeding doors make it awkward to reach the back of the tank for maintenance.
If you do any significant tank maintenance, a glass canopy is easier to deal with because you simply lift both panels off completely. Full plastic hoods require you to disconnect any cords running through the back notch before lifting, which gets tedious during water changes.
Equipment Cutouts
The rear edge of any hood needs cutouts for your heater, filter intake, airline tubing, and other cords. Glass canopies handle this with a removable plastic spine piece that you can notch yourself to fit your specific equipment. Full plastic hoods come with pre-cut notches that may or may not line up with your exact equipment placement.
If you're running a hang-on-back filter on a 20 long, measure the filter's intake tube diameter and the distance from the tank edge before buying. Some HOB filters on a 12-inch-deep tank put the intake tube very close to the center, and if the hood cutout doesn't accommodate that position, you'll spend time improvising.
Condensation and Evaporation
This matters more than most beginners expect. A 20 gallon long without a hood can lose half a gallon or more to evaporation per day in a warm, dry environment. Over a week, that's significant.
Glass holds up better to condensation than plastic. Water condensing on the underside of a glass panel beads up and runs back into the tank. On plastic, it can collect at seams and drip onto the light housing, which accelerates deterioration of plastic hoods with built-in lights.
For planted tanks running CO2 injection, a tight-fitting hood also helps retain CO2 near the water surface where plants can use it more effectively.
What to Budget
Glass canopies for the 20 long run $20-40. Adding a quality LED light brings the total to $60-130 depending on what your plants need. A full plastic hood with integrated LED runs $35-60 but limits your lighting options.
For a basic fish-only or low-light planted setup, the Aqueon Versa-Top glass canopy plus a Nicrew LED is a $55-65 combination that works reliably. For a planted tank wanting flexibility, plan for $80-130 total between a glass canopy and a better LED fixture.
For chiller recommendations if you need temperature control for your 20 long, see the Best Chiller for 20 Gallon Aquarium guide.
FAQ
What size hood fits a 20 gallon long aquarium? A 30 x 12 inch hood. Hoods labeled "20 gallon long" or "29 gallon" typically share this footprint. Confirm the exact dimensions before buying because some brands use slightly different sizing.
Can I use a 20 gallon high hood on a 20 gallon long tank? No. A 20 gallon high hood is 24 inches wide, while the 20 gallon long tank opening is 30 inches wide. The hood won't span the full width, leaving a gap on one end.
Do I need a lid if I have a low-light setup? If you're keeping fish that jump (most tetras, rasboras, and danios will jump when startled), a lid is not optional. Even calm fish will occasionally jump when alarmed, and finding a fish on the floor is a common beginner experience. Beyond fish loss, a lid also meaningfully reduces evaporation and the mineral deposits that form on uncovered tank edges.
How do I cut the cord notches in a glass canopy? The plastic spine piece on most glass canopies like the Aqueon Versa-Top can be notched with basic tools. Use a utility knife or a small hacksaw to cut notches sized to your cords and equipment. Most aquarists make multiple small notches and adjust as they add equipment.