45 gallon fish tank: dimensions and equipment

A tall three-foot tank: the 30 gallon’s footprint at nearly 24 inches high.

At 23¾ inches it is one of the tallest standard tanks for its footprint, and its floor is no bigger than a 30’s. Light fades quickly with depth, so plants at the bottom need a strong light, and cleaning the bottom glass takes long tools.

36¼ in long12⅝ in deep23¾ in high
See front view

PRO QuietFlow Power Filter 30 shown for scale. Positions and waterline are approximate; the checks below still apply.

Plan equipment for this tank →

Outside size of the Aqueon Standard 45. For the water it holds, measure inside the glass.

What lives in a 45 gallon

187 fish and invertebrates in our guide fit a 40 gallon tank as adults. Here is an example group drawn to scale, then the most popular choices.

All fish for a 40 gallon →
To scale: 8 harlequin rasboras, 6 bronze corydoras and a pearl gourami at adult size. An example group; check your own fish in this tank.

This tank, its lid and its stand

Tank format
Aqueon Standard 45; 36¼ × 12⅝ × 23¾ in outside
Empty tank weight
69 lb
Matching lid or top
Not published
Lid fit
Aqueon’s 2026 catalog lists hinged glass tops for its other standard sizes but none for this one. Measure the ledges the lid rests on, the brace openings and the room for accessories, and choose a top sold for a 36 × 12 in tank.
Matching stand
We haven’t matched a stand: use one the maker approves for this tank.

These sizes are for the Aqueon Standard 45; another brand’s 45 gallon can differ. Lids fit a tank model, not a gallon number.

Box sizes won’t tell you if a lid fits: measure the ledges the lid rests on, the openings either side of the center brace and the space for the strip at the back. Check the lid is the one made for this tank before you fit it.

Work out the filled weight → Add your substrate, rock, equipment and stand to see the total on the floor.

What to buy, in order

  • Buy the lid made for this tank (see below) and a stand built to carry it full, with room to open the cabinet and reach your equipment.

    Check stand and lid fit →
  • Choose gravel or soil and how deep you want it, then work out how much to buy from the inside size of the tank. Bags of different substrates weigh differently, so a pounds-per-gallon rule is only a rough guide.

    Work out how much substrate →
  • Check the filter is rated for 45 gallons and that a hang-on-back’s intake or a canister’s hoses reach the deep water.

    Compare filters →
  • A sponge filter needs an air pump, airline and a check valve; choose a pump strong enough for your water depth. A hang-on-back or canister filter doesn’t need one, though a battery air pump makes a good backup in a power cut.

    Set up an air pump →
  • Decide the water temperature your fish need and how cold the room gets. Size the heater from the maker’s chart and your actual water volume, and check it with a separate thermometer.

    Size a heater →
  • Check the light spans your tank and how it mounts. For plants, compare PAR at your water depth where the maker publishes it; watts alone don’t tell you how much light reaches the bottom.

    Check light fit →
  • Get a kit that tests ammonia, nitrite, nitrate and pH; most master kits leave out GH and KH, so add those if your fish need them. Dose conditioner for new water by the bottle’s label.

    How to test your water →
  • Use a siphon long enough to reach 2 feet down, and check you can lift what you take out.

    Choose water-change tools →
  • Keep plugs dry and labeled, with a drip loop on every cord as the manuals show. If you add a battery backup air pump, test it before you need it.

    Set up the power safely →

Then set it all up, step by step, and cycle the tank before you add fish.

Checkmarks aren’t saved when you leave the page; print it to keep them.

Measure before you buy

Outside arrows include glass and trim. Measure between the inside glass faces for water volume.
The water stops below the rim, and gravel and decor take up some of the space, so your tank holds less than its size suggests.
  • The tank’s outside size and the stand it needs.
  • The inside size up to the waterline, and how much room gravel and rock take, for your actual water volume.
  • The rim trim, the gap to the wall, the lid openings and where the light mounts.
  • The cabinet opening, the hose route and room to lift out filter media.
  • How you’ll carry water, the bucket size and where the outlets are.

With those numbers, use the water volume calculator and the electricity cost calculator. The first-year cost calculator keeps a line for every supply, even before you know its price.

Filters rated for this tank size

The smallest filters their makers rate for a 45 gallon, one of each kind. Compare the space they need and the upkeep, then choose for the fish and plants you plan to keep.

See every filter →

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Drawing of an aquarium filter (not a photo of the Aqueon PRO QuietFlow Power Filter 30)

Aqueon’s catalog rates this item for aquariums up to 45 gallons.

Aqueon PRO QuietFlow Power Filter 30

Aqueon’s five-stage hang-on-back filter: a NoDrip floss cartridge with carbon, a Bio-Holster and Bio-Media grid for bacteria, and a slot for a specialty pad (ammonia reducer, carbon or phosphate remover). Its pump needs no priming and starts again by itself after a power cut.

Consider: Aqueon doesn’t publish the flow or the power for this filter. If running cost matters, choose a model that lists them.

Drawing of an aquarium filter (not a photo of the Fluval 207)

Manufacturer-rated for 20–45 US gal aquariums.

Fluval 207

Small-to-mid external filter with separate maker ratings for pump output and filter circulation.

Consider: At 16.5 inches it is nearly 3 inches taller than the 107 on the same footprint. Measure the cabinet height plus room to lift the motor head out before choosing it.

Drawing of an aquarium filter (not a photo of the hygger Biochemical Sponge Filter, Medium)

hygger suggests it for 20–55 US gal aquariums under 19.7 in deep, with an air pump of 2 W or more.

hygger Biochemical Sponge Filter, Medium

An air-driven sponge filter: bubbles from an air pump draw the water through a dense sponge and up through a chamber of ceramic bio media, and the water comes back with oxygen in it. It has no motor of its own.

Consider: The flow is too gentle to catch fins or baby shrimp, but it needs an air pump, airline and check valve, sold separately, and it sits inside the tank.

Photo credits

Real photographs from Wikimedia Commons, resized and cropped to fit; each is used under the license named.