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Algae Attacks Newbie?

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Firstly, thank you to everyone who shares their knowledge here. I have spent hours reading posts over the last few weeks and it's been a great education for me.

I have a 17ft swim spa, so it's bigger than a hot tub but smaller than a pool. Volume is about 2000 gallons. Bromine system with a chlorine generator. Bought it last August. Lots of fun, no major issues.

From my reading here I have learned a few things that demonstrate how bad the advice was from the pool store after installation..live and learn...

- my FC levels have always been low (1 or lower). The advice of "check it once a week" with a test strip is clearly not enough for a bromine swim spa that is in the sun. Whatever FC is generated from adding oxidizer burns off that day. Weekly checks leave many days where FC was probably very low.

- the generator is a nice idea but it really can't keep up with both bather load and sunlight combined.

- I have since switched to using Clorox as my oxidizer , putting it in basically every night, using the pool calculator to target an FC level of 5. Hit it over the last couple of days so I am getting a feel for that. The water was slightly cloudy before I moved to Clorox, it's clearer now.

The possible algae...

- I started seeing what looked like small globs of dirt on the bottom of the spa last week, a week or so after a pool party the kids had (heavy bather load)

- tried cleaning the filter etc but it persisted

- created a basic siphon using tubing from the local hardware store..it tends to break up very quickly into a wispy sort of cloud but was able to get most of it out...but it returned overnight each time.

- pool water is otherwise clear, easy to see the bottom, crystal clear when you go under water with googles on.


- because I learned my lesson too late and low FC levels have occurred, plus 4 kids using it a number of times on top of regular bather load, I have to think Algae is a real possibility.

- given I have a bromine spa I think I have two options

1- shock using instructions I have found in these forums. I would plan to add enough bleach to take FC over 10 and watch for overnight loss. I have a test kit on the way, they are not as easy to find in Canada. Question- given I have a bromine spa, any alterations to the usual a shock instructions I need to know?

2- I could dump the water. Since it's essentially a big spa and not a pool, a water change is an option. But...if it is algae a simple water dump won't solve the problem I would still need to shock I would think, so I am not sure this option gets me very far.

I am open to other thoughts and input. I kick myself for not getting educated sooner but I believed the idea that I had a "self cleaning" spa and did not pay enough attention to water chemistry., plus the guidelines I were given really seem woefully inadequate given all that I have learned on these forums. I have found the learning here very beneficial, it's more than I have ever learned from the pool store folks, and I am moving towards using the simple products outlined in the BBB method to manage my water.

Thanks all, advice appreciated

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Some updated info

- when I arrived home from work last night there was some of the same gunk in the bottom of the swim spa, but not as much as a day a go

- I siphoned it out, brushed the walls, and added enough bleach to get free bromine up to 5 (it had fallen to zero in the sun all day)

- I also put most of the sections of the hard cover on as we are expecting a storm here today

- this morning, there was a lot less of the gunk in the bottom....makes me wonder if perhaps it's just pollen I am dealing with as the cover being partly on may have shielded the water from falling microscopic debris

- on the other hand, my bromine reading went from 5 to about 2 overnight...I say about because I am stuck with test strips at the moment and I can only make a best estimate based on colours on the stick.

So as I've steadied my bromine level I have seen less gunk, but hard to say if the cover contributed to that (pollen) or the higher sanitizer level has inhibited algae growth for the moment.

I am going to do another bromine loss test today as the cover is now fully on ahead of the rain so there is no sunlight getting to the water. I added enough bleach this morning to drive bromine up to about 10. Will see how it looks tonight.

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Yes, you could have pollen. Get a skimmer sock for the skimmer. If it's pollen, a lot should collect there. Pollen feels squishy whereas algae feels slimy. You can also easily see the difference under a microscope where pollen is typically round and spiky while algae is translucent and usually oblong.

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IMO i would not use test strips, they are sometimes not as accurate as liquid drop test kit, which i see you said you ordered a test kit. Also check the cyanuric acid/ stabilizer, If it is low (below 80 ppm) then by raising it you will be protecting the chlorine from the sun rays.

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