I'm using cured rock and cycled water. I see 30 days as over kill in this situation.

Do you have any sort of mechanical filter on this tank? That's what I thought you were talking about, but Myka's right, if all you've got is a glass box with fish in it, it will never cycle, and even with regular dosing of ammonia binders, and frequent water changes the water quality would fall rapidly and would impair your fish's health long term. If your'e only using a couple small pieces of rock and powerheads for water movement, I would be worried that over time your water quality is still going to suffer.

It's for my breeding project. No sump. Each compartment will have an Aqua Clear 30. It will keep the tanks isolated from each other.

So mechanical filtration, Yes.

Is it ok to leave rocks in a breeding system?

when you have no liverock and no sand, where do the bacterias settle?

My guess is there will be very little bacterias present to do the filtration. Also one good thing about porous liverock is that it will do a good amount of anaerobic filtration thus getting rid of a lot of nitrates as well.

How can one do a fish only aquarium without this as filtration? you will need to do lots of water change probably and monitor ammonia and nitrites and add something like Prime or AmQual to remove it.

Like I answered in your PM, you need some sort of biological media, be it live rock, live sand, bioballs, sponges...something. Otherwise there is not enough area for nitrifying bacteria to colonize to be able to keep up with the ammonia output from the fish and food waste.

Live rock in a Clownfish breeding system? Some people do, many people don't. Generally cost is a limiting factor. I wouldn't use sand though because that just gets in the way of bottom siphoning detritus and food waste. You will be feeding them much more than you would reef fish, and 20-40 ppm nitrate will become the new "clean". ;)