roots submerged in water, please help

I am growing in a 20 gallon tank with two air stones and pumps, I have a metal halide 250w lamp for 4 plants of which the tallest is about 24 inches. I have kept the light on the entire time, and am about to switch to 12/12. The roots are dangling out of the bottom of the pots submerged into water, I've been told to cover the tank so that light does not get to the roots and I'm still wondering what eles I need to do. I also have some red stems and an algae problem. some wilting leaves also. I'm going to get a 250w hps light soon, to run both the metal halide and the hps at the same time during flowering, any help would be appreciated, thanks.

Is it me or do they *seriously* be crying for more light?
Do please get that 250W HPS or more! That 250W MH looks too focused to me. (others please chime in. Looks like a good grow waiting for that ultra tip)

Looking stretched to me.

Get more light and closer.

(take a peak at my grow log, thats under a 150W HPS though started with a 70W HPS under a 24/0 lighting schedual)

u defenitly need more light!!!! andi think ur leaves have burn tips becuz u got to high of nuts... but im still learning, so get more advice.

By the way these guys probably meant to answer your question, don't worry about the roots in the water they are Happy to be there especially since you have a air stone in there. AND Yes you need WAY more light or you will harvest nothing from those. Windows usually aren't enough. well maybe not way more but a different reflector would do the trick sir. and cover the outside of the tank with cardboard easy fix.

Roots in water is fine, its kind of like DWC. You have a few improvements to make. first off you should cover the top of your perlite media so that light does not get in and cause algae. Algae will not grow in the dark. You also want to cover your tank so light isn't getting to the roots either.

Remove your bowl looking reflector and get a wide angle hood or a flatter piece of polished metal to "unfocus" the MH light. once its unfocused it won't present nearly as much radiant heat into such a narrow area, you will be able to get the light much closer. Put a fan blowing across the bulb and you can get even closer. Your plants are a bit stretched due to lack of light, and you can clearly see that the plants are searching for the light as they turn the top toward the highest intensity. Get light closer and remove that "Bowl" reflector. Even the bare bulb would be preferable to the bowl.