Can you refrigerate Nute water? lol

As long as the water isn't cold enough to shock the plants and if the PH level remains normal, I don't see the issue. Also iirc nute water should be thrown out after 6-7 days from mixing date.

 

I use an extra air line and stone to keep a bucket of top off nutes beside my cabinet bubbling away. Depending on what's going on in the overall grow it may be mixed to half or full strength. It'll last as long as your res does if you keep a lid on it.

At the end of the week, after the last top off I dump it and fill with fresh tapwater to bubble overnight. The next day I use that water to do the res change (now that the Chlorine in the tapwater has evaporated) and go from there, topping off the bucket as required and keep it for the week of res refills.

 

What kind of nutes is it? I see no real reason your nutes should be going bad in the jug less there is a lot of heat or light.

My suggestion would be yeah it's fine to keep it in their if you want long as the water isn't getting colder then 65F. Like said above adding air to the water is nice, or get a spray pump that you can just shake and pump air into it and store at the same time.

But also keep the nutes away from light after mixing( I dont know what you are using) as this will effect it as well.

 

If you're in the US, we don't treat with chlorine anymore. They treat with chloramine now and it doesn't evaporate off and there isn't enough of it in the water to harm your plants. We've been using straight tap water here for years with no problems. I believe in Europe they still use straight chlorine and have to let the water sit overnight. But unless you're in Flint, MI, your pretty safe. TWW

 

Ah the mad scientist approach, nice