Photo: Chris Penny · CC BY 2.0
stocking · freshwater
Stocking a 5-gallon tank
A 5-gallon tank holds one betta, or a colony of cherry shrimp, or a single snail. It does not hold a school. Here is what fits, what to skip, and the gear that keeps a small tank steady.
By Fishy Dave · Published 2026-10-11
Planning a different size? Try the stocking calculator.
Most starter kits are 5 gallons with a cartoon fish on the box. It is the size that fits on a desk and carries to the sink in one trip, and that is most of what it has going for it. Five gallons is a small tank with little room for mistakes, and it holds one animal plan. Pick a betta, a shrimp colony, or a snail, then run it well.
Everything below matches the stocking calculator and the species pages. If you are choosing between sizes, a 10-gallon tank gives you a few more options and more margin.
What fits in 5 gallons
Three plans work. One male betta. Ten cherry shrimp. One nerite snail. A betta with a single nerite snail also passes the calculator, and so do ten cherry shrimp with one nerite.
Only the betta, the shrimp, and the snails list 5 gallons as a minimum. Every other species on this site lists 10 gallons or more. That is why the calculator offers a single betta at 5 gallons and nothing else with fins.
One betta, set up properly
A betta in 5 gallons needs a heater, a gentle filter, a lid, and a cycled tank. Hold the water in the mid-to-upper 70s °F. A 15 to 25 watt adjustable heater covers a 5 in most rooms, and a thermometer on the glass tells you if it is working.
Use a sponge filter or a baffled hang-on-back so long fins are not pushed around. Add live or silk plants, with a leaf near the surface where he can rest and reach air. Keep a tight lid with a small gap, since bettas jump.
Change 25 to 40 percent of the water each week and test between changes. Feed a few pellets once a day, or split that into two tiny meals, and net out what he leaves. Overfeeding fouls a 5 faster than anything else you will do. The feeding guide has the details.
A shrimp colony instead
Start with ten cherry shrimp in a cycled, planted 5. A smaller group makes it hard to see them, and a few early losses can wipe it out. Use a sponge filter so shrimplets stay out of the intake, and keep moss or fine-leaved plants for cover.
Copper kills shrimp. Check the label on any medication or fertilizer before it goes in the water. Cherry shrimp also need some mineral hardness to molt, about GH 6 to 8. Pour new water in slowly at the same temperature, because a swing in water chemistry is a common reason for a failed molt.
Do not add fish to a shrimp tank in the hope of balancing it out. Almost any fish eats shrimplets, and a betta plus a colony is more waste than a 5 can carry.
Snails, and how many
A nerite snail is the easy add. It cleans film algae off glass and decor, and the eggs it lays will not hatch in freshwater. Plan on about one snail per 5 to 10 gallons, so one is the number. Nerites climb out of the tank, so the lid stays on.
A mystery snail also lists 5 gallons, but it makes more waste than a nerite, and a 10 is kinder. With a betta in a 5, the calculator allows one, but only just. Pick a nerite unless you specifically want the bigger snail.
What does not belong in a 5
Goldfish, common plecos, angelfish, and anything that gets large are out. So are the small schoolers people reach for, including neon tetras, guppies, and zebra danios. Chili rasboras and ember tetras are tiny, but both want a 10-gallon tank and a group of ten or more. In 5 gallons that group becomes too many fish in too little water.
A single schooling fish is not the fix either. A lone tetra or rasbora is stressed and hides. Fish that need a group need a bigger tank, and the answer is to pick one of the three plans above.
Why a 5 is less forgiving
Five gallons dilutes almost nothing. One day of overfeeding can push ammonia up, and a heater that sticks changes the temperature in hours. Cycle the tank before you add anything, using the cycle guide, and add the animal only when ammonia and nitrite read zero.
Test weekly with a liquid kit and change water by nitrate, not by the calendar. If nitrate climbs past about 20 ppm between changes, change more water or feed less. The water change guide covers the siphon and the dechlorinator. If fish are already in and ammonia is climbing, the new tank syndrome guide walks through what to do today.
If you find yourself wanting a second species, that is the sign you want a bigger tank. Stepping up to a 10 is the cheapest fix, and the betta tank mates guide shows what a betta can share once there is room.
Gear that makes a 5 workable
A few listings we would open for this job. Skip anything you already own that still works.
25W adjustable aquarium heater for 5 gallons
The usual rule is 3 to 5 watts per gallon, which lands at 15 to 25W for a 5. The 50W heater on the heater page is a 10-gallon pick and is too much for this tank.
Put a separate thermometer on the glass and trust it over the dial. A small tank swings faster than a big one, so check it for the first few days.
See this listinghygger sponge filter, small
Air-driven foam gives a betta soft flow and keeps shrimplets out of an intake. It also holds a lot of bacteria for its size.
Needs an air pump, airline, and a check valve. Squeeze the sponge in old tank water, never under the tap.
See this listingAPI Freshwater Master Test Kit
Five gallons has little water to dilute a mistake. Liquid tests for ammonia, nitrite, nitrate, and pH show a problem before the fish do.
Freshwater only. If the bottles you already own are in date, you do not need another kit.
See this listing
Frequently asked questions
What can I put in a 5-gallon tank?+
One male betta, a cherry shrimp colony of about ten, or a single nerite snail. Those are the three plans that match the species pages and the stocking calculator. A betta with one nerite snail also passes the calculator's waste check.
How many fish can you keep in a 5-gallon tank?+
One. A male betta uses most of what a 5 can handle by the calculator's waste math. Shrimp and snails are the way to keep more animals in the tank, because they produce much less waste.
Can I keep a betta with other fish in a 5-gallon?+
No other fish. A snail is the one safe add. Shrimp are a gamble with a betta, and a betta plus a shrimp colony is too much waste for 5 gallons by the calculator. See the betta tank mates guide for what works in a larger tank.
Can neon tetras, guppies, or other small schooling fish live in a 5-gallon?+
No. Neon tetras, guppies, zebra danios, chili rasboras, and ember tetras all list 10 gallons or more, and the schooling ones need a group of six to ten or more. Five gallons cannot hold that many fish. The 10-gallon stocking guide covers what does fit there.
Is a 5-gallon tank big enough for a betta?+
Yes, as a minimum. Heated, filtered, and cycled, it works. Ten gallons is easier to keep stable, but a well-run 5 beats a bowl by a wide margin.
Can a goldfish live in a 5-gallon tank?+
No. A single goldfish needs about 30 gallons and makes far more waste than a betta. Five gallons would foul within days.
Does a 5-gallon tank need a heater?+
For a betta, shrimp, or snail, yes in almost every home. A small tank loses heat quickly. Aim for the mid-to-upper 70s °F for a betta and the mid-70s for cherry shrimp, and check with a thermometer.