UV filter ???

I bought an 8 watt sterilizer on ebay (no pump--$30) and attached it to the cheapest little water pump ever. It completely cleared up my green water, shockingly well, actually. It takes a couple of days for the dead algae to get out of the water but the result is crystal clear water (and a bunch of green slime in the filter).

I ran it for a long time without problems (a few hours a day on a timer). Later I disconnected it and the green water didn't come back, so I leave it off now.

The only potential problems I am aware of:

1. Some people say it can break down iron fertilizers into a form not easily available to plants, so they don't recommend using it within a day or so of dosing iron.

2. It can break down flourish excel, if you use this. You shouldn't use it within a day of dosing flourish if you can avoid it.

3. Depending on how you set it up, it may add another unsightly tube or powerhead. But of course it's less unsightly than green water is.

If I got mine for $30, then $25 doesn't sound unreasonable for yours.

The science behind a UV filter is not new or expensive technology. They also make quite small UV bulbs, that are plenty intense for killing things in close proximity.

Three of the main factors with how effective a UV is, are contact/exposure time, intensity, and period of use.

If you only use it once a week to kill single cell algae, the odds of it preventing disease or parasites is slim. If you use it every day, you may have fertilizer issues (apparently- I'm not sure how well backed that is)

If you have a lower intensity bulb, you need higher contact time (or a smaller volume of water to sterilize). Typically, this is increased by slowing the flow rate.

I really don't see any reason why this option you found wouldn't work.

I also don't see any reason why most are ~150 dollars....except that we pay it.

If you don't mind, post a link of the one you found.