Nitrate & nitrite both high

[Percyfish]

Hi all
Relative newbie pond owner - 3.5 years in, 3 x goldfish added after 6 months, one baby survived first winter, approx 30 second winter (gave 12 away, but no idea on exact numbers remaining!), no babies last year (phew!). Unknown how many have over-wintered. I test with a basic strip test once a month, never any issues, but the last 3 days I've got high nitrite and nitrate. The test pack says 'water change' - but it's a pond so easier said than done! I did a sludge suck, cleaned the filter and refreshed the zeolites, dosed with 'aquasafe' as well incase that helped. No food for 4 days now.
But it's still reading high The fish have vanished (it's an above-ground pond so deep with a couple of stools in that they hide under).
I'm just stumped as to next steps! Do i really need to be emptying the pond and refilling??

 

[WaterGardener]

You don't need to empty the pond. A partial water change could help if the temperature of the newly added water is close to the existing water temp in the pond.

Add more plants if you possibly can. They will use the nitrate and can help to lower that.

You can bind the nitrite and nitrate with Prime. That will keep the nitrite from affecting the fish. Used for that purpose the Prime will last for 48 hours and will need to be dosed again. Keep doing that until the filter is able to convert all the nitrite to nitrate.

Test strips are not very accurate and they start to deteriorate the minute you open the container and expose them to the air. The liquid tests are much better and we recommend using those.

It seems that your pond is starting a new nitrogen cycle and is in the second faze where the ammonia is being converted to nitrite, and that to nitrate.

More plants or water changes are the only ways to lower nitrates. You just don't need or want to change all the water at once, putting more stress on the fish. Better to do that in smaller amounts more frequently.

 

[TheFishGuy]

Agree with what watergardner said.

More plants for the water filtration, and a partial ( 25 or 50% ) water change could also help.

It is also possible your test strips are simply inaccurate, and if you are using them every week I would recommend a drop test kit.

 

[Percyfish]

Thanks both. I'll do a partial change tomorrow. I usually only test monthly (or when i remember, to be more accurate!), this is the first time anything has been 'off' so has thrown me! Glad i don't have to empty the whole thing. There are plants in there but they're all sunk at the bottom, ready to reappear when the water warms up a bit (a couple are just starting to be visible). I've tried various things but the fish tend to eat them. The biggest plant is dying back currently (I'm removing dead bits as they come off).

 

[j.w]

and welcome @Percyfish