How to Lower Nitrate in a Goldfish Tank, by Freshwater Fish World on YouTube. 7 min 30 s.
- Video length
- 7 min 30 s
- Time to do it
- 30 minutes
- Difficulty
- Easy
- Steps
- 8
What you need
Steps
Test the tank water with a liquid nitrate test kit. Shake the bottles exactly as the instructions say, then compare the colour against the chart and write the reading down.
If nitrate reads above 40 ppm, change 30 to 50 percent of the water. Treat the new water with dechlorinator and match it to the tank temperature before adding it.
Vacuum the gravel with a siphon while you drain the water. Push the tube into the gravel to pull out trapped waste, which is where much of the nitrate comes from.
Repeat a 30 to 50 percent water change every two or three days until nitrate drops below 20 ppm. Never change all the water at once, as the sudden shift can stress goldfish.
Cut back feeding to what the fish clear in about two minutes, once or twice a day. Remove any food left on the bottom with a net or turkey baster.
Rinse sponge and filter media in a bucket of old tank water, not under the tap. Replace only half the media at a time so the bacteria that process waste survive.
Add fast-growing plants such as hornwort, elodea or pothos roots in the tank or filter. They use nitrate as food and help keep levels down between water changes.
Test nitrate once a week and keep a log. Once levels are steady, do a 25 to 50 percent water change every week and check the filter is running properly.
Tips and common mistakes
Do not panic and swap all the water: a big sudden change in water chemistry can shock goldfish more than high nitrate.
Keep the filter running and never wash it in tap water, as chlorine kills the bacteria that keep nitrate in check.
Feed less rather than more, because uneaten food and fish waste are the main source of nitrate in a goldfish tank.
Goldfish are messy fish, so avoid overstocking and give each fish plenty of water volume.
Questions
What nitrate level is safe for goldfish?
Aim to keep nitrate under 20 ppm and treat anything above 40 ppm as a warning to do a water change. Test regularly because goldfish produce a lot of waste.
Will a bigger filter remove nitrate?
Not on its own. Standard filters turn ammonia into nitrate, so you still need water changes; some filter media and live plants can help use up nitrate.
How often should I test nitrate?
Test once a week in a stocked goldfish tank, and more often if the water looks cloudy or the fish seem unwell.
This guide was drafted from the video's details and general task knowledge. It has not been checked against the full video. Check the video and relevant product instructions before following a procedure. Report a correction.
