The density of the algae determines the flow rate. Thicker the algae the less the light penetrates the water so the slower the water has to flow past the light. So it varies year to year. You can turn down the water flow by say a 1/3 and see if that clears the pond in 5-7 days. Once clear you can turn the flow back up. You can also remove the water and replace. Another algae bloom will no doubt happen but slow enough for the UV to keep up so you never see the bloom. UVs are meant to keep a clear pond clear. They have to be way over sized to handle an already very green pond at max flow rate. The cost of the bigger unit and all the electric needed is lot compared to just changing water once. But many people do buy bigger units. Global warming is our kids' problem, not ours after all.

I can tell you that I have two Savio UV lights (57 watts each) in my Savio skimmerfilter and they have never done the job for me. They are advertised by Savio as being the size needed for my pond and are the largest they sell but just do not keep it algae free. I just bought a new UV from a fellow threader (150 watt) and we will see if it cleans up the problem. I have to tell you I have given this some thought and my pea size brain tells me that it just makes sense when you stop and think about the difference in UV's and how they operate. The Savio filter type sits in the skimmer next to the skimmer basket and is mounted vertically. The one I bought is in line and sits horizontally. Now with that in mind I pictured a match stick floating in the water and then passing by the vertically mounted Savio UV's. It would pass by it in a fraction of a second. That same match stick would have to float the entire length of the horizontally installed UV (almost 6 feet) taking a lot more time. Which would be affected by the UV light more? Naturally the horizontal so it just makes good sense which one would work best. At least that is, to my pea brains way of thinking. I will let everyone know for sure after my sons and I install the new one and it has had a chance to work. Here is a link that might be useful: My pond the way it was before the freeze.

Mike, Thanks for the heads up with the EA UV for the Savio. I know you've had a lot of trouble with the UVs so I'm sure you know all about them. My Savio is post-recall and I've had tremendous results with it, running it only a week here and there at times. I'm sure if a homeowner truly had a problem with a Savio UV, post recall, that this would make for a nice lawsuit. It would be hard for me to imagine a better setup for a UV than the private chamber utilized in the side of the Savio skimmer. It is just a nice design - and it works for me. I'll look into the EA UV unit when it becomes time to replace my bulb/lamp. Vickie, I feel I'm right ahead of you on your issues since you're doing roughly the same thing I did last summer, and we are using some of the same equipment. You are correct in thinking that our climate and setups are going to be perfect for all kinds of algae growth. We'll get algae early in the year, pre-spring for sure when nothing else is growing and the water temp is cool. Then because it is a new pond you'll have the algae out competing the young, small plants you pot in both your bio-falls and pond. It will take weeks for the bio-filter we have to even come close to doing a job on the extra nutrients our water has... and it still won't keep up except once you get tons of submerged or floating aquatic plants established. Mikes recommendation on WH is a good one but unlike him I wouldn't worry too much about the fish mixing w/ the WH because with that size bio-falls you're going to need all the extra filtration you can muster! I would put them everywhere you can, or are wiling to accept, and then fertilize them the way drh1 recommends, search stump remover - I use Gordon's, because last year without it my new pond only did so-so with the WH and I think it was because they didn't have any extra help. This year with David's (drh1) recommendation of a tspn a week they are absolutely thriving with big long floating roots (filtering). Now even though I seeded my biofalls media with Microbe-Lift several times last year I was still having some green water. It went pea-soup green about six days after the initial filling. Then it went CLEAR overnight about six days later. But because my bio-falls box, same as yours, isn't so big and the plants outside of it not so established I started to get a little green water again and some string algae on my stream and rocky areas. I got the Savio UV from www.practicalgardenponds.com and added it to my skimmer box and it really did well, for me. I still battle the string algae but I'm resigned to that fact since it is largely a problem of lack of fine filtration. I've changed out my filter media (was lava rocks) in my bio-falls a couple of weeks ago, going to Springflo media instead (started over on the biofiltering as a result). I'm cleaning my prefilter in my skimmer more often, sometimes when I add H202 or stir-up the mulm in the pond I'm cleaning the pre-filter twice daily, just depends. I also added some activated charcoal to the skimmer box recently. Because I was trying to get a hold of the string algae problem I may have had more and more mulm accumulating on the bottom of my pond, or maybe even having some of it become suspended in my water and floating; so, I did add a Pondcare product known as Accu-Clear to help bind the small particles together and I think that has helped with filtration and water clarity. I'm just hoping that with a couple of good sweep-outs of my pond, yes sweep as in using a broom, I hope I can get ahead of the detritus that accumulates. And I have to say, I fear for you in as much as I see you have installed a rock bottom to the pond. I know there are many that do but I would be too worried that this is going to make maintenance tougher. I think that it is smart that you stay proactive with insisting on relatively clear water because having particulates and other growths floating around makes it harder to get back to that CLEAN SLATE look you started with in the beginning. Good Luck, I hope that some of this information can be used to your advantage.

Albert, Yes do not look at the bulb either directly or looking through the water inlet or outlet. Depending on the bulb and the distance that your eyes are from it will determine how fast it will burn your eyes. It can burn your eyes in less than a second. You may not know that you have burned your eyes when it happens. It will show up that night when you are sleeping when you wake up with your eyes burning. Depending on the unit that you have you could be right or your wife could be right. Some units have either a pressure switch or a flow switch built in so the bulb will not come on unless the unit is operating. These are usually the better units. Unless you check a bulb with a meter as Sandy said or can actually see a break in the filament you can not tell if the bulb is bad. Just because the bulb is black in the filament area does not mean the bulb is bad. That black color can happen in a very short period of time. Most likely the ballast is burned out and needs to be replaced. Bigstan is correct in that manufacturers usually rate their UV based on the output of bulb at what they determine to be the end of the life of the bulb. This is normally when the output drops to 80%. Most bulbs hit this point at 9000 hours of use. But there are other things that will affect these numbers. One thing is if the bulb is turned on and off a lot. These bulbs are designed to be turned on and left on and turning them on and off a lot will shorten the life. You also have to look at the size of the unit, the flow rate of water through the unit and the location of the pond. As an example I have one client that has an Emperor Aquatics 120 watt high output unit on a 2000 gallon pond. This unit is so over sized for the pond that if the water flow rate through the unit is set for the pond size the output of the bulb could get down to 20 or 40% and still keep the pond from turning green. I have also seen units on ponds that were too small for the pond and would only work when bulb was close to 100% output. Then there are manufacturers that rate their units so high that they can't possibly work even when they are new. Mike