Fish water is good for plants. It contains nutrients like nitrogen as well as micronutrients which will help your plants grow. In addition, it may have beneficial bacteria which is also helpful for plants. I found articles that recommended fish tank water for tomato plants, house plants and gardens and none that said it was dangerous.  You should be fine.



Most aquarium algae is harmless and thus it would be safe to eat your vegetables. However, blue-green algae is really a bacteria. Harmful cyanobacteria and the toxins they produce are usually in lakes, oceans and other bodies of water, but aquariums can produce them. Most are blue-green in color, but some may be yellow-green, red or even purple. Some produce an awful smell, but some don’t. I couldn’t find a definitive way to determine if you have cyanobacteria. I learned that algae taken out of water can live some time as spores so there’s no guarantee removing it from water will kill it. Chances are you had a perfectly safe kind of algae and your vegetables will be fine, but there is a little chance that you had a bacteria that looked like algae. For more information, you may wish to read: How People and Animals Get Sick From Harmful Algal Blooms | Harmful Algal Bloom (HAB)-Associated Illness | CDC , Aquarium Algae 101: Everything You Need To Know | Fishkeeping Advice or https://aquariumscience.org/index.php/16-aquarium-algae/.