nfinit1
12-28-2003, 3:09 PM
greetings all
I need assistance understanding why adding ferts NPK delays algae growth but helps plants growth
It seems to me that both should grow
Why is it????
Does adding Iron delay algae growth also???
How do water changes affect algae/plant growth??
Starry
12-29-2003, 4:26 PM
Well, since no one else is tackling this one....
Algae are less fussy than plants, so they will flourish even when the conditions aren't good enough for plants. But, if you add enough nutrients and light for the plants, they will grow faster and become healthier. Healthy plants outcompete algae, and there are also complicated processes where plants actually release chemicals that inhibit algae growth. Kind of like the fry of some fish species, where the strong ones inhibit growth of weaker ones. But you don't really need to go into that. The take-home message is that happy plants equals not-so-happy algae. You can't get rid of algae if the plants aren't growing well.
Water changes are good all around, in particular for fish. I don't know how familiar you are with Diana Walstad's book, but I personally don't like it and don't agree (I'm not alone). We only test for a very very few compounds, but there are thousands building up in old water. Like with hormones released by fry, as I mentioned before. You just can't guess what's going on, so water changes are always a safe bet. Also, when you're dosing heavily, you're not always testing for everything (potassium and traces in particular, we dont' test for), so they could build up to toxic levels. Frequent water changes help reduce the level of trace metals that the plants may not be using as fast as we're dosing it.