My largest Oscar tank (a 120) has pH 7, GH 5, KH 4, KNO3 13 and P 5
(I can not measure over 5ppm with my Hach low range kit.
I am thinking of moving 5 gallons to the 55 once a week to supplement
P and KNO3. That would be cheap....free.
Any reason this would not be plausible?
I think someone else here was planning to do this. Maybe they'll de-lurk and
tell us how it worked.
As long as the oscar tank is healthy, I see no reason not to try it.