Thanks JCO - I really do appreciate all the help you've given me up to this point. I think the problem is probably with the pH buffer (I think it's called KH???)......which is allowing such huge swings in pH from day to night.

I also have a theory (although I don't know if it's true......you can give me your thoughts), but if a system has TOO MANY PLANTS, then they could add more CO2 into the water at night time which, depending on how many plants you have, it could really impact the pH swings.

So I am thinking of cutting back on some of my plants with hopes that it will not cause the pH to swing so wildly. Aside from that (and the additional aeration I've already done), I don't know what else to do.

I read about buffering the KH of the water, but I don't know if that's a good idea, nor do I want to keep messing with a system to make it worse. I am hoping that somehow, someway, it will naturally equalize and stabilize.