From Roseman DIY DWC thread: Spider Mites - Spider mites are not insects but are more closely related to spiders. These arachnids have four pairs of legs, no antennae and a single, oval body region. Most spider mites have the ability to produce a fine silk webbing. Spider mites are very tiny, being less than 1/50 inch (0.4mm) long when adults. Spider mites have tiny mouthparts modified for piercing individual plant cells and removing the contents. This results in tiny yellow or white speckles. When many of these feeding spots occur near each other, the foliage takes on a yellow or bronzed cast. Once the foliage of a plant becomes bronzed, it often drops prematurely. Heavily infested plants may be discolored, stunted or even killed. Web producing spider mites may coat the foliage with the fine silk which collects dust and looks dirty. Spider mite species seem to be warm weather or cool weather active pests. Adult females usually lay eggs on their host plants. The eggs hatch in days to weeks into the first stage, called a larva. Larvae are round bodied and have only three pairs of legs. The larvae feed for a few days, seek a sheltered spot to rest and then molt into the first nymphal stage. The first nymph now has four pairs of legs. The first nymphs feed a few days, rest and molt into the second nymph. The second nymphs feed, rest and molt into the adult stage. The males are usually the size of the second nymph and have pointed abdomens. The females have rounded abdomens and are the largest mites present. Most spider mites spend the winter in the egg stage but the twospotted spider mite over winters as adult females resting in protected places.
Solution - Early detection of spider mites, before damage is noticed, is VERY important. The tiny spider mites can be detected only by a full and thorough leaf inspection (on both sides of the leaf). If you find Spider Mites you must act fast and hit them hard with either a bleach solution (1 tablespoon of bleach to 1 gallon of very hot 95°F, pH balanced, water in a spray bottle.) Hydroponics Stores also sell Neem Oil and other remedies for spider mites.
Or one of the best things to do is get a bucket of HOT water and make a combination of neem oil and safer soap or additive free dish washing soap. You want the water to be warm so that the neem oil will break apart and mix throughout the water. DO NOT dunk your plants in until the water has safely come back to room temperature.
The safer soap will not only act as a wetting agent to help coat the plant but also weakens the exoskeletons of the lil buggers. The neem oil will make them immobile so they cannot move and suffocate them.
Dunking is the most effective method while they are smaller because it coats everything from the ground up, but this is a very effective spray. You should spray every three days, the undersides of the leaves or dunk every three days depending on size. This is the most eco friendly and safest method of treatment. This is what you should try first.
keep up the good work! 
