Betta tank cleaning schedule
Fifteen minutes a week, a filter rinse every couple of months, and a short list of things people do faithfully that make the tank worse.
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Weekly: fifteen minutes
- 01
Prepare the new water first
Fill a clean bucket, dechlorinate, and let it come to tank temperature - or match it with warm water and check with a thermometer. New water going in several degrees off is a real stress, and in 4.3 gallons a two-gallon change at the wrong temperature moves the whole tank.
- 02
Dose the dechlorinator on the new water
Seachem publishes 5 mL of Prime per 50 US gallons, so a 50% change on a rated 5-gallon needs about 0.22 mL. Use a 1 mL syringe. Treating the new water in the bucket is better than dosing the tank, because the chlorine never meets your filter bacteria at all.
- 03
Siphon out 25-50%
Move the siphon over the open substrate rather than digging into it. You are lifting the debris that has settled on top, not excavating the bed - a deep dig releases what you were trying to remove and disturbs the bacteria living there.
- 04
Wipe the front glass
A magnet cleaner or a cloth kept solely for the tank. Never a household sponge - detergent residue is lethal in a small volume and very hard to rinse out.
- 05
Refill slowly
Pour onto a plate, a bag, or your hand rather than straight onto the substrate. Then check the thermometer once more.
The dosing, per tank
| Tank (rated) | Actual water | Prime, full volume | Prime, 50% change | Stability, day one |
|---|---|---|---|---|
| 3 US gal | 2.6 gal | 0.26 mL | 0.13 mL | 1.3 mL |
| 5 US gal | 4.3 gal | 0.43 mL | 0.22 mL | 2.15 mL |
| 10 US gal | 8.5 gal | 0.85 mL | 0.43 mL | 4.25 mL |
| 20 US gal | 17 gal | 1.7 mL | 0.85 mL | 8.5 mL |
Every two or three months: the filter
When the flow visibly drops - not on a calendar - rinse the media in old tank water, in a bucket. Squeeze the foam a few times, put it back, done.
Never under the tap. Chlorine kills the bacterial colony and the tank re-cycles from scratch with a fish in it. This is a common way to lose a fish in month three and it always looks like it came from nowhere.
Never replace all the media at once. If a foam block has genuinely disintegrated, run the old and new together for a month so the colony transfers.
Monthly, or when something looks wrong: test
Ammonia, nitrite, nitrate. In an established tank the first two should be zero and the third should be somewhere under 40 ppm and stable between changes.
Write the numbers down. A single reading tells you almost nothing; four weeks of readings tells you whether the tank is stable, drifting or heading for trouble. This is the single highest-value habit in the hobby and it costs a notebook.
The things people do that make it worse
| Common practice | What it actually does |
|---|---|
| Rinsing filter media under the tap | Chlorine kills the colony. The tank re-cycles with a fish in it, and ammonia appears within days. |
| Replacing the filter cartridge monthly | Throws the colony in the bin every four weeks, so the tank never fully establishes. Buy a filter with rinsable media instead. |
| The 100% water change and full scrub | Removes the bacteria on every surface at once. This is the classic bowl-keeping routine and it guarantees the tank never cycles. |
| Deep-digging the substrate weekly | Releases trapped waste into the water column and disturbs the bacteria living in the bed. Skim the surface instead. |
| Topping up evaporation and calling it a change | Topping up replaces water; it removes nothing. Nitrate and hardness concentrate steadily. They are two separate jobs. |
| Chasing pH with adjusters | Produces a swinging pH, which is worse than a stable one at the wrong number. Bettas adapt to a range; they do not adapt to a moving target. |
Topping up is not a water change
An open-top nano tank can lose several per cent of its volume a week to evaporation. Only the water leaves - everything dissolved in it stays behind, so nitrate and hardness climb steadily even in a tank you top up religiously.
Top up with dechlorinated water for evaporation. Change water separately for waste. Doing only the first is a very common reason a tank slowly deteriorates despite apparently diligent maintenance.
When the routine changes
During cycling: different rules entirely. See the cycling page.
After adding an animal: test more often for a fortnight. Any increase in bioload needs the colony to catch up.
If ammonia or nitrite is ever detectable: change water immediately and daily until it is not, and find out why. That reading is never normal in an established tank.
In a heavily planted tank: nitrate rises more slowly because the plants are consuming it, and you may genuinely be able to move to a change every fortnight - but only on the evidence of your own test readings, not on the theory.
What we would buy for this
Chosen from the same registry as our roundups, on published specifications and the arithmetic they imply - not on testing we have not done.
Seachem Prime
The dechlorinator whose published dosing makes it the obvious nano choice: 5 mL treats 50 US gallons, so a 5-gallon water change needs half a milliliter. A 100 mL bottle is therefore roughly two hundred water changes. It also binds ammonia and nitrite, which is the property that turns a cycling accident into a survivable week.
Skip it if: You need something you can dose by the capful into a nano. At this concentration a capful in a 5-gallon is a ten-times overdose - you are measuring in drops.
Seachem Stability
Bottled nitrifying bacteria with a published seven-day schedule, which is what makes it useful rather than mysterious. Seachem publishes the exact dose: one capful per 10 gallons on day one, then one capful per 20 gallons daily for a week. In a 5-gallon that is 2.5 mL then 1.25 mL - a bottle lasts a very long time.
Skip it if: You expect it to replace cycling. It seeds bacteria; it does not conjure a biofilter overnight, and Seachem does not claim it does.
Frequently asked
How often should I clean a betta tank?
A 25-50% water change weekly in a cycled, filtered tank. Filter media rinsed in old tank water every two or three months. There is no full clean.
Should I take the fish out to clean the tank?
No. Netting and moving a betta is far more stressful than a partial water change it can simply swim in. The only reason to remove a fish is a treatment that requires it.
How do I clean the gravel in a betta tank?
Move the siphon over the open substrate to lift settled debris, rather than digging into it. Around plants, skim only - disturbing roots does more harm than the trapped detritus does.
Can I use tap water for a water change?
Yes, dechlorinated and temperature-matched. Treat it in the bucket rather than dosing the tank, so the chlorine never reaches your filter bacteria at all.
My tank is cloudy after a water change. What happened?
Usually disturbed substrate, which settles within a day. If it is white and persists for days it is a bacterial bloom, which typically follows over-cleaning or overfeeding. Test for ammonia, feed less, and do not clean harder - that is usually what caused it.