How much of a water change at end of cycle with huge nitrate levels?

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Hi all
I think I’m nearing the end of my cycle - Ammonia 0 and Nitrites 0 after 24 hours - however for pretty much the entire cycle my nitrate levels have been between 20-50ppm and are currently easily over 50ppm (which is as high as the Red Sea test kit reads) as it’s turning dark purple almost instantly.

Due to the extreme levels of nitrate how much of a water change should I do at the end of the cycle? I’m thinking a small amount won’t cut it?

Just some info incase it changes things, in the tank (Fluval Evo Sea 13.5) I have:
10lb live sand
3.5 kg live rock
3kg dry rock
Few ocean fossils

Standard filtration for a fluval system (carbon, biomax, filter foam) as well as the ps2 protein skimmer that’s made for the tank.
Also running a bag of chemi-pure on recommendation which has only been in the tank 2 days and added a Hydor Koralia Nano wavemaker for extra flow.
Current sg is 1.020 which will be improved to 1.025 at the end of the cycle for corals.



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Reply #1

You need to change enough to bring nitrate back down to acceptable levels ,a single 90% water change would bring 50ppm back down to 5pppm


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