Recommended Water Change Schedule

[SaveThemAll1]

HI ,So there's a 400 L tank with 23 goldfish:3 are about 25 cm, 4 are about 15 cm and the rest are less then 10 cm. I want to hear your opinions on the WC scheduale reccomended, is 25% once a week is too much? please share your opinions, thank you!

 

[DaleM]

HI ,So there's a 400 L tank with 23 goldfish:3 are about 25 cm, 4 are about 15 cm and the rest are less then 10 cm. I want to hear your opinions on the WC scheduale reccomended, is 25% once a week is too much? please share your opinions, thank you!

If anything, 25% weekly would be too little. Goldfish have a massive bioload and you're overstocked with 23 of them if they are all to remain in there.

Your nitrates help determine your water change schedule. Once they start getting above 20ppm, it's usually time for a water change unless your tank is densely planted

 

[2211Nighthawk]

Oh boy. That’s about 100 gallons. 10”, 6”, and 4” for people like me who hate metric. I can say right now that tank is massively overstocked. I’m assuming they are common/comet goldfish based on the size. I hope you got a pond or something to move them too because they will never thrive in a tank that tiny. I do 50% on a 65 with a 6” (pretty sure he’s 7” now) goldfish and my nitrates are still on the high side by the next weekly change.