Help. Black algae & RCS die-off???

pabearpa

All
Could use your help with the following:

20g long (since 5/2010);
Marineland Penguin bio-filter system;
plastic plants / live plants / moss wall / driftwood;
11 fish / used to be ~25 RCS.

Just recently, black algae (long, hair-thin strands) started growing on the plastic plant, driftwood and one of the live plants. At the same time, the RCS started dieing off. Not sure if they are related?

Here's today's readings:
Temp = 78
Nitrate = 80
Nitrite = 0
GH = 150
Chrlorine = 0
KH = 40
Ph = 6.8.

I know the Nitrate is really high, but I don't know if it's the cause of the above AND / OR how to correct??

Your assistance / advice would be appreciated!
Pabearpa

aunt kymmie

I wouldn't think the the algae would be the cause for RCS die off. High nitrates could be a possibilty. Why are they so high? If it was me (and it's not) I'd set up my tank maintenace schedule so that they never went over 40. As far as the algae- what type of lighting and lighting schedule?

LisaC144

+1. 80ppm is high and can cause stress and die off of sensitive fish/inverts. Below 40ppm is ideal, but the lower the better. What is your water change schedule like? How often and how much?