Hi Derek,

I'm hoping you can help with this problem I am having.

After my WC, my water starts to turn green, and by about day 4, it is VERY green... to the point where I cannot see from the left side through to the right anymore.

On Friday I did a 80% waterchange, and introduced Purigen into the filters.

This has not helped at all (Altho it does help with the wood tannins.)

I was about to start a 3 day blackout today when I noticed my Angel's eggs have turned into wrigglers. (I don't hold up too much hope for them being in a community tank, but I'd like to give them a chance.)

My ammonia/Nitrites are both at 0ppm. Nitrates are at 5ppm. Tank is 285 litres, with 60w T8 lighting.

I believe this problem is an algae spore that is growing in the water.

What would you suggest I do to try clear up the water? Or should I look at doing a blackout soon? Can I do a blackout with the wrigglers in?

Seems strange that you are getting algae problems with nitrate levels that low. 
See if someone you know has a nitrate test kit and see if the readings are the same.
Just remember that by doing a water change with algae problems, you are aggravating the situation by adding more nutrient to the water and helps with the algae bloom. Try adding some good activated carbon to your tank for a few days

Not aware of "purigen" product. What is it suppose to do?

Take out the ancistrus/pleco that you have in the tank to give the angel fry a chance of survival before switching off the lights
Also take out any other nocturnal fish that you have in the tank.

There was a daphnia filter used for koi ponds in the UK at one stage. It runs through a container with daphnia in it that feeds on the green water that passes through it. So yes, if you put the daphnia in a net and circulate the tank water through there it should work.

You might also want to try an algicide which should also clear up the problem.

Personally, as far as the Purigen goes, I would just use a good quality activated carbon.

Stupid question! Do you switch off your lights at night!! What food you using? Some of the cheaper foods are over dyed. I use Tetra. Rod

Where do you live and what water are you using?

Bit of  a concern when you say that the carbon does not clear your water. Means that there is something wrong with the carbon and sounds like it is already fully utilised. Just remember there are different grades of carbon. Activated carbon will absorb impurities from the air also,. As Seachem is a good brand name, I doubt that it is a poor quality activated carbon, so I would think that it is already utilised and needs to be replaced.

There are test kits available for testing phosphate.