Managing algae III

Things quickly went from bad to worse.

I coupled a water change with manual removal of a large amount of various kinds of algae. I dug through my collection of 'aquarium stuff' and found an (old) bottle of Seachem Flourish. Great; although it's not marketed as an algaecide, it often works. So I added some. Then I realised that what I had wasn't Flourish Excel, and rather than adding a carbon source, I was adding fertiliser. Not what I was thinking, but it should still boost plant growth, and hopefully would help them compete with the algae.

Already on Friday (the day I did the water change) I noticed that they water wasn't terribly clear; by Saturday it was noticeably more cloudy. The algae on the driftwood was also growing like crazy, and I removed a lot more of it. Saturday evening I visited the pet store in search of Flourish Excel and found instead API CO₂ Boost. Since it's basically the same stuff (glutaraldehyde) I decided to buy a bottle and see how it would work. I added my first dose that night.

By Sunday, it was obvious that something was wrong. I had a growing green water problem (overgrown of unicellular green algae). Over the next few days I kept dosing with the CO₂ Boost, and the water kept getting greener and greener.

By Tuesday afternoon the water was very green and cloudy.

On Thursday it was bad enough that I decided to stop the experiment and do a major water change.

Wednesday, 11:40 am

Wednesday, 4:14 pm

Thursday, 11:58 am

As I started to refill the tank I added dechlorinator to the water I was about to add, together with the  CO₂ Boost and, without thinking, the fertiliser. Then it occurred to me to wonder what was in it. A quick glance at the bottle clued me in to the likely cause of my green water problem - the first listed nutrients were N and P. Just what you don't want in a tank with a green water problem. At that point I realised I had a problem.

After the water change, things looked a lot better, but the water was still green (upper image). Less than an hour later, the water was noticeably greener.

Normally, the best course of action is to fix the problems with the water, but in this case it didn't seem like the most viable solution. I had elevated the levels of phosphate. It would probably have taken several water changes to get it back to something like the baseline level.I decided, instead, to dig out UV Steriliser. A UV steriliser uses ultraviolet light to kill microorganisms in the water. I bought it many years ago to fight ich (quite successfully) and hadn't used it in years.

Within a few hours, there was a visible improvement in clarity.

Two hours later, further change was visible.

The following afternoon, things have improved even more.

Afternoon of day two, and the water clarity is better than it even was.

By the morning of the second day (Saturday) the water was pretty much clear. Saturday afternoon, 48 hours after I started running the UV steriliser, and the water clarity is as good as it have ever been in this tank. I'm really impressed with how quickly it managed to get the job done. Granted, a 24 W unit is overpowered for a 55 gallon tank. But it did the job remarkably quickly.