What I'm asking is why you said this. What is that you think is out of whack? I'm trying to figure out where you are. This fixing pond thing is 80% trying to understand what the person thinks is true and trying to explain where they took a wrong turn. The pond stuff is the easy part.
No.
Air temps? Water temps?
A couple of months ago I was flying on a major airline and I was talking to the flight attendant and she asked if I wanted a tour of the cockpit. Sure, why not. I get the nickle tour and the captain asks if I want to sit in the co-pilot seat while he takes a break. Sure, why not. The captain is explaining this and that. So then he says he's going to hit the can and tells me to take the stick. I tell him I don't know how to fly and he says it's easy, just keep the stick steady and don't touch again thing else. I figure he must know what he's talking about, so sure why not.
So I'm tooling along at 35,000 feet and 457 mph ground speed. But the plane slowly starts to bank right. At first no big deal I turn a bit left. But I guess I turned a bit too much and now I'm banking left, and I notice I'm down to 27,000 feet although I hadn't notice I'd pitched the nose forward. OK, now I have to pull up some and turn right. So I give it a go, but now I'm banking way right and pretty soon the plane is upside down and I'm loosing altitude fast. OK, now I'm pretty confused. Upside down and heading for the ground at around 700 mph, how to I fix that?
So in this little fable the plane is the pond, the passengers are the fish, I'm the person looking for advice and the captain is the "expert" giving the advice. Who's the biggest idiot? The passengers aren't. Am I for for allowing the captain to talk me into this mess? A little. But the biggest idiot is the "expert" captain. Why in the world did he think I could fly a plane? Why would he give me advice like "just hold the stick steady" and not give me a 500 hour course on all the things that can go wrong and out to fix it before going to the can? Because he's an idiot.
I don't want to be that idiot. So I don't like to tell people stuff that will kill their fish if I don't have any idea about what is actually going on. And along that same line, if a pond keeper is unable, for whatever reason, to take water tests and report the values with some precision they aren't going to be able to do the necessary calculations and tests needed to fix the problem. The best advice I could give is "don't do anything" and hope the fish luck out.
I'm not saying I'm giving up on you natbla, just saying if you want really to figure this stuff out and have any chance of getting it right it's going to take some effort and attention to detail. That's my advice for what it's worth.