I understand your dilemma now. Since it is not recommended to run aeration less than one turn over a day...running only at night could be risky.
What temps have poor effects on the speckled trout?
What ever that is...I would consider running the diffuser until the lower temps approach the high end of that range. Once they get there, I guess you should shut down and hope for the best.
I am not very experienced with pond meistering, but you not getting much attention as of yet and hopefully someone with actual experience in this situation will pipe up soon.
