Waterbug;
I don't want to dispute scientific fact, and I'm not saying anyone is wrong, but I've observed an interesting "phenomenon". For about seven years now, I've been looking after a garden center's pond division, and every year we get our hornwort from the grower about ten days before the water hyacinths are ready, so I fill two identical fibreglass tubs with water (pumped directly from three ponds used for irrigation purposes) and place the hornwort in one of them. When the hyacinths come in, they go in the second tub. Every year, without fail, the water in the hornwort tub remains crystal clear, but the water in the plant-free tub goes green within 24 hours. The only variable here is the plants. Am I missing something? Not arguing, mind you, just curious.
John