I would just let it overflow for a few more days as intarsiabox suggested. I don't know what it is but clearly some reaction has occurred in your tank. Another suggestion is to simply raise your skimmer a few inches. Create a shelf out of egg crate or PVC tubes. This will help with the overflowing and should allow you to adjust your skimmer water level better.

I've found that if a skimmer is too deep in water for its own good it can be more susceptible to overflow. Raising it can give you a larger margin for error and adjustability.

Yeah, that. ^ You don't mention using RO/DI water. Many dechlorinators/ammonia blockers will make skimmers overflow like mad until they are entirely out of the system.

It looks like that skimmer cup has a drain line on it. I'd recommend directing it out of the tank to a large bucket and keep an eye on it for a bit. It will start to drain your tank, but if there's nothing in it right now you don't need to worry too much about a mild fluctuation in salinity, and you can just add some salt to the sump as needed. If you don't have an ATO system that will replace what's lost with fresh water, you can just make up a batch of new salt water and add as necessary (though if you add something like Prime to the new water, it might just make it go nuts all over again). The bacteria won't care much about a small drop then rise in specific gravity, if one is even detectable.

Whatever is making the skimmer go nuts needs to get out of the tank. Dumping what ends up in your skimmer cup until it stops going crazy is the fastest way to the do that.

what i do when i treat my tank with chemiclean is i intentionally have my skimmer cup resting on the neck tilted with a huge gap so plenty of foam runs into the tank. this lets me skim the chemical out when under normal circumstances (cup fully on and skimmer already adjusted to driest setting) the thing overflows immediately. this will let you get whatever it is, out.

Yup I only use ro/di water

Actually my water chamber for the skimmer is pretty deep. Not home to measure as of right now but I would say it's about 14" or so. I did try to physically lift my skimmer higher up n held it there n the water lvl In the skimmer did lower to the correct lvl. Wouldn't egg crates or pvc tubes make it super noisy by the pump vibrating.

I don't think I can do this cuz what's coming out into the skimmer cup is like 90% water and 10% water. Will prob fill a 5g bucket in about 5-10mins. My ato is currently on my other tank that I will swap over on the big swap day

Whoa.. I don't know about your specific skimmer, but 14" seems very deep to me. My last two skimmers have sat in about 6-8 inches of water. My newest skimmer I had at about 8 inches but then raised it another 2" by sticking two 2" pvc pips underneath it. I don't notice much additional noise. The water does a decent job of dampening. Plus my sump is enclosed in my stand.

if noise or vibration becomes and issue just try dampening with foam sheets (that you can get at Michaels. I have those under my other pumps (return and biopellet reactor).

Ya I made it deep CUZ I'm planning to use my final chamber in my sump as a frag tank/return pump so I needed it to be as deep as I can. Gonna take ur advice to use pvc n egg crate now

Yup, at 14" deep you'll never stop overflowing your skimmer. The vast majority of skimmers require 8-10" of stable water level to function optimally. Since this is going to require a long term solution, make sure your "box" is very sturdy or it may tip over or make a vibrating noise.

What should I use to dampen the vibration? Right now I'm cutting 4 pieces of pvc then prob cut some teeths under it so water can flow through to not trap crap later on n zip tie them to egg crates n put skimmer on up. But I suspect massive vibration

I'm having almost the exact some problem with my Vertex 200. It's been running now for almost 3 months. It's at 9 1/2" just like they recommend. I haven't added any chemicals or anything except for some vinegar dosing which I stopped a month ago. I still don't have it functioning right, the bubbles are usually more like when you add Alka-Seltzer/Eno vs what should be the nice slow big bubbling. I try not to adjust it much anymore, it's fine one time (rarely) then the next check it's overflowing like yours. If I used the drain adapter on my tank it would be fresh water in the matter of days. My old little Euro- reef skimmer would kick this things ass, but I paid so much dam money for this thing so just has to work right lol ? :lol: