It is imperative that you keep testing the water, two or three times a day. That way you know what is going on since the tank is way out of its normal equilibrium. Everything you are used to looking at as indicators will give you false input.
If the tank has a mini-cycle, your livestock (fish and softies) are usually going to be okay. Which is why I told you to dose Seachem's Prime into the tank. If you have an old bottle (more than a year), do your tank a favor and buy a new one. I believe it is one capful per 50g of water, so a bottle will go a long way.
Let's see pictures tomorrow, as by then the water will have cleared. Post your water parameters too:
pH
Alk
Salinity
Calcium
Ammonia
Nitrate
Nitrite
Temperature
We don't need to know about Magnesium or Phosphate at the moment. Since you run ozone, what is the ORP today? What is it normally?
Polyfilter needs to be run to absorb any metals from the tap water, as well as the crap that comes out of a water heater. We never use hot water because of the filth trapped within.
It sounds like you did all you could to resolve the situation the best you could. Keep up the good work.
PEX - ah. Totally different beast. There are compression fittings for PEX, but there is also a specialized wrench and compression ring system the bites down and locks the tubing to the various connections. Construction companies have been switching to PEX (both red and blue tubing) to avoid having thieves steal copper in the walls of new homes. Plus with PEX, you can make bends, using less connections. Neat stuff, but a little tough to work with.