I use my water garden water change water on my plants (where I have 2 Comets and 2 Shibunkins in there) - particularly the muck/detrius, which is essentially nitrates. If you have potassium stuff in the water, that should be okay for the plants, particulary since it's rare to find a high-potassium (the "K" in the "N-P-K" designation) source by itself other than the oft-recommend seaweed, etc.

Link below is to some of the precious discussions on this question. You might want to browse through them. Dave Here is a link that might be useful: Using aquarium water discussions

I tend to feel that just because aquarium water has some nutrients is not a good indicator it's necessarily good for your plants. Here's why: We know it's not complete and that it doesn't contain nutrients in a ratio that's favorable for plants. That means that using fish emulsion alone as a nutrient source will definitely limit growth (Liebig's Law of the Minimum). To prevent growth from being limited due to nutritional deficiencies, you'll need to supply either a soluble fertilizer or organic soil amendments, with the former being an easier and more reliable way of delivering nutrients. So here the aquarium water user is - wondering what nutrients he's supplied and what nutrients are lacking. With no way of knowing, he reaches for his fertilizer and applies it according to directions. This should deliver a dose of all the nutrients necessary for growth in a favorable ratio (if it doesn't you used the wrong fertilizer). This application makes the nutrients in the soil solution derived from the aquarium water redundant. They actually serve no purpose, and in fact, unnecessarily raise the the level of EC/TDS higher than if they were not present, making it more difficult (though marginally) for the plant to take up water and the nutrients dissolved in water, so you would have been better off w/o it - with sticking to a fertilizer plan you KNOW provides all the necessary nutrients at a favorable concentration and in a favorable ratio to each other. RG - your plant has obvious nutritional deficiencies. My guess, because of the interveinal chlorosis AND the cupping of the leaf margins is that it's short at least Mg, and very probably N and others. If you're willing to answer a few questions, I'm pretty sure we can narrow things down and get your tree back on track. Al

In as word : no. Vegetables need mucho mucho light. There should be -- at a minimum -- two 40-watt florescent lights, 48" long, suspended a few inches above the seedlings, moved up as the seedlings grow. Cabbages probably want to be grown as cool as possible, as well. A cool sunny window with a supplementary 100 watt incandescent (or the equivalent) in the evening would probably work also. My mother grew delphinium seedlings that way years and years ago in the old days before we had all this equipment at our disposal. I am not an expert vegetable gardener, but I imagine you would want to get those cabbages outside into the ground as soon as you ever possibly can. They are winter vegetables, no? The good news is that seeds are cheap and you can always try try again.