I use a wick system. It seems to work for me. Are you using plain water, or a nutrient solution? If you are using nutrients are they diluted for the new plants?

Maybe if you tried using gravel for the plants to grow their roots into, and just got a small pump and a cheap timer from lowels hardware, you could just flood the gravel every other hour or so. Put lots of holes at the bottom for quick drainage. Small pond pumps are not too expensive.

What is the Ph.....what is the EC.....how often do you change nutrient?

Forget the rockwool. Use a thin styrofoam sheet with holes in it for the support of the plants. Step up the areation of the water/nutrient mix. Maybe if you use a large plastic trash can as the main nutrient tank, and install a small pond pump to pump fresh nutrient up into the grow tank. A simple overflow drain hose could be installed in the grow tank to return the used nutrients back down to the main nutrient storage tank. I used a system simular to this several years ago with good results. chuck

child wonder I think I know what your problem is with your whole setup. I believe u said that you were using "rockwool". I have been doing literally hundreds of hours of research on the web looking at forums supplies and comments sites all sorts of stuff. I think I read somewhere that "rockwool" actually breaks down slowly once exposed to water over prolonged periods and the stuff that comes off of it actually affects your p.h. levels of your water. So either change to a different "growing medium" such as perlite or vermiculite or....check your p.h. every few days as needed.

I have a DWC system that I've been running for a couple weeks now with no problems. You can check it out on my blog if you like. It runs great. Just follow the link below and then click on the 'Blog' link on the right. It's buried in there under 'DIY DWC' or something like that, I forget.

Like the others here I'd suspect that the problem is probably something simple - light getting to the roots/medium can cause bad things to grow, too strong or too weak a solution can cause nutritional problems, improper aeration can drown plants... there's a lot of possibilities.

Try to get us as much information as you can think of.

Here is a link that might be useful: The Encyclopedia Hydroponica

I only grow my plants where the roots hang into a container of nutrients. I have many plants in rock wool, some in pumice, and some in hydroton or grow rock media.

The secret is maintaining correct PH, PPM while having a large flow of air coming out of the bubbler.

When I use rock wool cubes I drill a 1 1/2 hole all the way through the cube and place the roots in this hole. I wedge the top 2" of the plant tight at the top with spare rock wool parts, or use a rock wool plug. Ultimately the upper 2" of the rock wool cube holds the plant snugly at an early stage until the roots can grow into the cube.

With lots of air moving in the container, it looks like the nutrient solution is boiling. If you want a good way of doing this, here is what I have done and it works great and is not expensive.

Buy a 2 1/2 gallon bucket with a lid. Buy a 4" basket, and a 4" rock wool cube and plug. The plug should be 2" diameter. If you buy a cutting plug for the cube, make sure the cube has a hole cut in it or you will need to cut your own hole.

From the other side of the rock wool cube (opposite the side with the 2" hole in it for the rock wool plug) drill a 1 1/2" hole into the 2" hole. In the end you should have a 2" hole half way through the cube for the cutting plug, and a smaller 1 1/2" hole that connects to it from the other side.

Place the rock wool cube with the hole you put in it, into the basket. Make sure that the hole in the rock wool cube is not blocked by the basket. I cut a hole in the bottom of the basket as well.

Cut a hole in the lid of your bucket so that the basket will hang without falling in. I use utility scissors for this and it works fine.

Place a single 4" long blue air stone in the bottom of the bucket and connect it to a min of a 10 gal fish aquarium air pump.

Add your nutrient solution to the bucket and set the PPM and PH. Place the bubbler at the bottom and make sure that it looks like the water is boiling. Align the bubbler so that its main source of bubbles hits the center of the basket when it is installed in the lid of the bucket.

Place the basket with the rock wool cube in it into the hole in the bucket. The solution should bubble up into the rock wool cube through the hole cut into the bottom of it.

Put your plant into your rock wool plug and then put the plug into the 2" hole in the top of the rock wool cube. When you put your plant into the cube, make sure the roots hang down the hole you cut into the solution. If you have no roots, do not worry about this step.

Thats it for the construction part!

Check your PH daily. Find a chart online that lists the PH range of your plant. Start with the PH in the middle, and check the level 2 times a day. I do early in am, and then before bed at night before and after my grow lights come on. I also have a high air volume fan that circulates the air in my grow room. It blows the plants well enough that most of them self pollinate (except the Squash based plants).

I also buy a small plastic lid that I cut a hole into that I cut in half to prevent the solution from evaporating around the base of the plant where the basket is in the solution.

I hope this helps.

check the ph of the water that's probably your problem and also make sure that the solution your using is for the right stage of your plants life cycle