Kill brown water with UV

After 20 years in the reef keeping hobby, I was about to call it quits.  My 90 gallon reef tank, setup since 2000, was giving me a problem that I couldn’t fix.  The problem you ask, was brown water.  Water so brown that I couldn’t see my fish unless they swam near the front glass and I wasn’t sure if my rock was still in the tank.

A little history first

Around February of this year, I replaced the single Current USA Orbit Marine IC pro light with two VIPARSPECTRA 165 watt led fixtures.  My corals basically stopped growing after I installed the Current USA light and a single Current USA light wasn’t enough for a 24 inch tall tank.  Even though it looked great, I needed something brighter.

The VIPARSPECTRA’s are much brighter in comparison and I was getting ready to start adding corals again around April but I noticed an increase of brown algae growth that looked much like cyano.  I didn’t think too much about it but it started to get progressively worse as time went on and around June the water was brown after the first couple hours that the lights were on. 

Water changes didn’t fix it

Around the second week of August, I started changing water.  I would normally change around six gallons at a time in the past but this time, I did an 18 gallon water change.  The water looked better the next day for about six hours but then it started to turn brown again.  Thinking that the water change might have helped, the following weekend I did another 18 gallon water change but it only a lasted a couple hours after the lights came on the next day.  The third week, I did one more 18 gallon change and the next day the tank water was brown after about an hour when the lights came on and it got progressively worse over the following week. 

I am guessing that the nutrients in the clean salt water was feeding what ever was causing the brown water.  I couldn’t do more than an 18 gallon water change with my current setup and I concerned that anything bigger might cause issues for my 20 year old clown fish and my 11 year old powder blue tang.

Then the (UV) light bulb came on

Many years ago, not long after I started this tank, I installed a UV sterilizer.  I didn’t have a problem at the time when I installed it but I was all about the technology back then.  After a couple years of using it, I took it off because I wasn’t able to clean the sleeve inside.  I cannot say that it helped or not but I didn’t really think much about it for many years since then.  

I started looking on the reef keeping forums for brown water in salt water tanks and saw a couple comments about some others suggesting a UV sterilizer to battle brown water.  I didn’t want to buy a new unit just going on a hunch but since there were at least a couple other people suggesting it, I ordered a unit from Amazon.  

The unit I ordered was a 15 watt Aqua Ultraviolet Advantage 2000+.  I was a little disappointed when it arrived because I realized that I paid $130 for a little plastic tube with a power supply and bulb but I had to give it a chance or send it back and consider my exit plan from the hobby. 

It wasn’t the easiest to plumb in my already tight stand and sump but with $20 in vinyl tubing, a Maxi Jet 1200 and some various plumbing parts, I installed it last night.  I didn’t expect to see any improvement in the few hours that my lights were still on but I was hoping that I would see some improvement in a few days to a couple weeks.  

What a difference a day makes

Today, when the lights came on, the water looked better than it has over the last few months but I was waiting for it to turn.  My wife told me, that about two hours after the lights come on is when the water would change to brown.  Today, after four hours, the water was not brown.  After six hours, it was still not brown and as I type this, after nine hours, the water is still not brown. 

I never would have thought that within 24 hours, the UV would have worked enough to allow me to see in my tank after months of brown water.  I am not sure how well it will work long term but it’s looking better after only one day. Needless to say, I am pretty impressed and I will update this post to see if it keeps the brown water away.

Brown water on 9/02/18

Could hardly see my fish

not brown water

24 hours after UV on 9/03/18





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