Hello you are correct your algae has died and has left water Brown. Quick and easy way to clear your water of organics. Get a milk crate line it with hundred percent polyester batting. The kind you stuff quilts with. Place 1000 to 3000 gallon per hour pump in it. I used bungee cords to secure it. Stuff as much as you can in there submerge it and let the pump run. Check it every 2 to 3 hours. The white polyester will turn Brown pull it out of the pond throw it away add new white polyester batting and put back into pond and submerge it again keep doing this within 24 hours your pond will be clear.. while you are doing that make sure that you have some key things in place good filtration rotate your pond at least twice an hour so you should have a minimum of $3,000 per hour pump rotating water through some kind of Bio Falls you can add pea gravel or rocks or lava rock to increase the filtration. Add aeration (oxygen) to the water very important. This should get you through the first two parts of the nitrogen cycle. The last is nitrate in the nitrogen cycle and you will need lots of plants for this. You can do floating or you can just put potted plants in the pond. You can take cannas very heavy feeders place them in a pot with pea gravel stick it in the pond. You can consider doing a bog add on down the road but in the meantime you need to get plants in there. Crate above will solve iyour problem pretty instantly. I have a koi pond the bog and a waterfall filtration system. Clear to the bottom. However I also have an unfiltered frog pond to which I only use one aerator to add oxygen to the water. It too is clear to bottom however since it only has passive Boggs on the shelves there really isn't any filtration system and the bottom get nasty so a couple times during the summer I do the crate trick and it works like a gem. Hope this helps on your way to Clearwater. You can also add bacteria for Jumpstart I recommend night out 2 by micro lift. However you will need to turn your uv off until established. I don't use UV lights good luck