I don't understand why people have problems germing seeds in rockwool? I've never had a problem since the first time.
This is what I do and it works.
Drop the seed in a cup of tap water overnight. I don't get in a hurry, I put the cup in a dark place and sometimes they soak for up to 36 hours or whenever I get ready to put them in the cube. Seeds will sink when they are ready. I would not soak them forever, Overnight works and up to 36 hours works. I would not go any longer than that.
I get my Pargro Quick Drain cubes wet with tap water. Drop the seed in it. Lately I've been putting a touch of potting soil on top of the hole. Not much. Not pressing it in too far. Just so the seed is not exposed. It worked fine before I started doing this as well. I place it in like a jar lid with a small amount of water in it and put it in a window sill if it's not cold at night like the winter time. Otherwise put it under a CFL. At this point the cube is pretty drenched, but, the water in the jar lid should evaporate pretty quickly. I don't soak the cube in water from the jar lid after this point. The jar lid is merely there to catch any runoff. Don't let the cube dry out, but don't drown/drench it anymore either. Just keep it moist.
If I do Hempy or soil. When the seed pops, I put that sucker in a HEMPY solo cup, just perlite with a hole near the bottom and water it. If the conditions are acceptable I put it the window sill.
I use plain tap, last time I checked several years ago, my tap runs PH of 7 and PPM under 100. It does not need to be watered everyday. Just touch the top of the cube. Maybe put a few drops of water directly on the cube if it seems dry. Don't overwater and drown it. Moist.
When I went hydro and a couple of times when I used hempy, I merely placed some hydroton in a solo cup and put water into it up to about the bottom of the cube. Again, move the hydroton out of the way everyday and check with a fingertip to see if the cube is moist. A few drops or a milliliter of water on the cube if its dry. Don't drown the cube. Moist. Not drenched.
When it's grown a true set of leaves maybe 2 weeks later or less, I go to the final container be it hydro, Hempy or soil. By this time it may already have been taken out of the window sill and is growing under a CFL. I don't really think about it, at this point it's like whatever. Just needs some light and to stay moist. I've also just let it sit in the window sill for a couple of weeks after repotting if the temp and other conditions are good. Like spring and summer time. Then place under a small desk lamp or hanging light at night. 24 hours of light is fine at this stage. 18 or whatever. I don't understand why people lose seedlings unless they are bad genes or peeps are just loving them to death.
That's it. The only issues I have are if there is a lot of moisture at the top of the solo cup, it can turn the medium green. So, try to avoid that. Although when that has happened to me the green will disappear once you final pot.
I've used the jiffy pellets as well. Same system but, I wouldn't use those in a hydro system where the little bits of soil could clog up any small holes in a drip ring or whatever.
I've had some Lemon seeds soaking in cubes, jiffy pellets and small soil containers for a little while now. They sit in a plastic container, but, I do not keep water in the bottom. I have only watered the tops of the medium once. Like in a couple of weeks. They could take up to 40 days to germ. They will not be put in the sun or under much light until they pop. To avoid the green.
Granted, this is just a tried and true method. I am sure I could expedite the growing process by experimenting with adding Nutes or whatever, but Im a micro guy. I don't have a schedule or deadline to meet. Tried and true brings me success.
Test your tap water. It may not be suitable for you to do it my way. Improvise and get you some filtered water if necessary. Even then, I just fill up a 5 gallon water bottle for .30 a gallon and used to do this the whole grow. Until I discovered that my tap water works fine through the whole grow. Yours May not. Your temps/humidity may be different than mine. You have to improvise and dial in your method to suit your conditions.
The moral of the story is keep it simple stupid works.