I had a similar problem with tannins in the same size pond. I used 1 quart of activated charcoal (~$12) wrapped in burlap stuck inside my biofilter so that the water had to flow through it. It only took a couple of days to work.

the verdict... i went to speak to the folks at the mountain horticultural research center in asheville, nc and they gave me the info i was looking for. we did a par reading this morning at about 10. the ambient reading was 560.4 micromoles/second/metersquared. two readings from behind the glass averaged 476. this indicates about a 15% reduction in photosynthetically active radiation. while it would not be ideal to use glass like this for a large commercial operation, the gentleman i spoke to seemed confident that i could design around the 15% shading for my personal use greenhouse. i plan to use a different material for the ceiling and possibly the east/west sides. this will allow for much more light than if i were to solely use the tinted windows. i still want to build a cold frame this winter as an experiment, but i am pretty sure that this can work. the par meter provided an instantaneous reading (15 seconds). as a matter of reference, most commercial growers require an average of 15 moles of light/heat energy per day. when we did our calculations, estimating only six hours of sun, my glass would provide between 9 and 10 moles per day. this number is significantly lower than what commercial growers would look for, but i think that my greenhouse location will recieve more than 6 hours a day, even during the winter months. maybe i will have to supplement with some artificial light in the winter, i will only find that out once the greenhouse is operational. pat tea... i would suggest doing what i did and contact your local horticultural research center to do a par reading. seems that this is the only way to really know what types and amount of light are allowed to pass through your glass. the combination of the tint and your location might not be the best. i live in western nc and it is super sunny here the majority of the time, even in the winter months. we have a naturally long growing season. i don't know if the cloudier weather in the pnw would pose an issue, but that is something you might want to talk to your local researchers about. i spoke to a number of folks before i went to the research center - glass manufacturers, tinting companies, even the greenhouse companies that were referred to in a previous post- and no one really had any solid info to give me, only their personal opinions or another reference. other than getting a par reading done, the only other option seems to be building a cold frame. practically speaking, this would be the best way to experiment, it will just take a full winter to know your results. good luck with it, i hope you can use those windows. free glass rocks! thanks to everyone for your ideas and suggestions... now on to design ideas. who's got some for me?

Car windows' tint is just a film that's put on the window, so it's easily removed. House windows have a tinted reflected coating to keep out the UV rays that can't be removed. It's usually a neutral grey and doesn't affect the color of the light and is rarely even noticed.

My husband and I are very much "do-it-yourselfers" but when we had our 4 large floor to ceiling windows and sliding door tinted we elected to have a pro do them. In order to get a smooth finish, that lined up correctly with the glass without bubbles or wrinkles it was worth having someone install the film. I think it cost around 300$ (maybe less) for someone to install it. We used a three M product, and it has cut down the heat into the room considerably. We used a medium tint and yes the room became somewhat less bright but not at all dark. It has been a year and our eyes have adjusted to it and we think it was to blindingly bright before the window tinting. I would imagine the tinting will last a good long time unless my cat severely scratches it (in fact, the film was placed and integrated on the window so well that I can not see an area that I could even begin to remove it off the window).