When a macro algea dies, can it poison your tank?

[SadaAesix]

I had some turtle grass die off in my tank. I woke to find the tank, green so I did a 20% water change immediately.
Afterwards however my nitrates were 40 ppm. which is high for a right after water change reading.
I expect the dieing maiden's hair infused my tank with alot of nitrates and I hope nothing else. Should I be alarmed? Should I take further action?

[Amphiprion]

The turtle grass is a true plant, while the maiden's hair is an alga. When they die, they can release nutrients back into the water, but not really toxins (at least not in these species). I would do another good, reasonably large water change and add some carbon and you should be just fine. The above probably isn't even necessary, but it wouldn't be a problem to do it anyway (and may help if help is needed).