Tests show 0 Nitrates and Phosphates yet lots of HA in tank

[Rybren]

Here's something that has always perplexed me:

Testing shows undetectable Nitrates and Phosphates, yet hair algae is growing out of control. People will often state that the reason for undetectable nutrients is that the algae is taking it all up; therefore, there is none left to show up on the tests.

Okay, that makes some sense, but...

Other people will state that they run with 20ppm or 30ppm or more of nitrates, yet they don't have any hair algae in their tanks. Similarly, others will state that they have detectable levels of phosphate but no HA. There are also those who have detectable levels of both but don't have HA.

What gives? How can both of these situations be true? An inquiring mind wants to know.

Thanks

 

[Flamed_Razor]

My nitrates are near 40 ppm with .12 on the phosphates. Some people don't have HA because they have the magnesium level at 1400-1600. When I had HA I too bumped up my magnesium level 1400 and the algae went away.

 

[Randy Holmes-Farley]

Yes, all of those things can be true.

Algae must have all of N, P, iron, and other nutrients.
So algae can be limited by many things, including low nitrogen, phosphorus, iron, and being consumed by herbivores. Only one of those needs to be low for growth to be limited. For example, having 200 ppm nitrate is not useful to algae is the phosphate is 0.001 ppm.

If you have plenty of problem algae growth, then the algae growth alone is taking up a lot of those nutrients, and so that values may show up low on a kit.

Bear in mind that most kits are not very good at detecting low levels, and 0 doesn't mean none. It may still be above NSW levels and not have enough for many kits to detect. For example, surface phosphate is often as low as 0.005 ppm, which kits do not readily detect.

 

[Rybren]

Thanks Randy

The apparent contradiction of those two situations always bothered me.

I knew that the detection limits of our hobby grade test kits was often not good enough to show very low levels. I hadn't thought about iron affecting the growth. In your opinion, are there other nutrients that could be limiting, and if so, do you have any ideas on how to reduce them?

My tank is about 5 years old and since the initial cycle has completed, I've never been able to detect nitrates or phosphates using Salifert and API test kits. I have had hair algae issues off and on - it seems to hang around for 6 months or so and then disappears for a year or more. My maintenance schedule doesn't vary - 10% weekly WC, bi weekly harvesting of macro and Xenia, occasional siphoning of the sand bed, etc.

I am currently in another period of HA infestation and have recently added an unlit 20G cryptic sump filled with 40lbs of live rock and just finished adding an algae scrubber. The tank is a 75G mixed reef and a 35G sump/fuge. I'm sure that the HA will eventually go away on it's own, but I sure would lik to help it on its way..

 

[Rybren]

Oops. The Image didn't embed and I can't modify my post. Sorry

 

[Randy Holmes-Farley]

I fixed it.

 

[Randy Holmes-Farley]

FWIW, I think that's a very nice tank!

I knew that the detection limits of our hobby grade test kits was often not good enough to show very low levels. I hadn't thought about iron affecting the growth. In your opinion, are there other nutrients that could be limiting, and if so, do you have any ideas on how to reduce them?

The problem with getting anything else limiting is that it may be low enough to limit other creatures that also need it (like corals and their zoox). IT would be a balancing act that might be hard in the absence of good tests for these trace elements.

Here's an article about Richard Ross's tank which is definitely not phosphate limited, but might be iron limited:

Reefs Magazine - Skeptical Reefkeeping IX: Test Kits, Chasing Numbers and Phosphate

 

[Rybren]

Randy,

Thanks for the fix, the compliment, the link, and your thoughts.

When I first made the switch from fresh to salt, one of the first resources that I found were your reef chemistry articles. I printed off every one that I could find and put together my Reef Reference Binder. I continue to add to it as I find more words of wisdom from THE Reef Chemist.

Thank you so much for sharing your wisdom and insight.

Happy Reefing!

 

[Randy Holmes-Farley]

You're welcome and thanks. Glad they were helpful.

 

[fishroomlady]

May I ask if the picture of your tank is with or without a HA problem? I think different people have personal ideas of what is considered a bad alage problem. I'm just curious. That is a beautiful tank! what are the large tan softies? devil's hands or toadstools or something else - love them!

 

[Rybren]

Thanks. The HA was just starting its current cycle when I took that picture.

If you are referring to the tan leather in the centre of the tank (with the clowns in it), it is some kind of toadstool but without a discernible centre stalk. That is a single leather. It is currently at least 12" in diameter. There is a pink cabbage in front o it and some kind of finger leathers off to the right. Thy keep dropping youngins all over the place.

The tank looked (to me) much better a couple of years ago, but there was a massive die off and I lost almost all of the corals (all of the fish and inverts survived)

 

[Cory]

I've tried an algal turf scrubber before and couldn't get it to grow until I started dosing iron.

I had an algae problem too and found phosphate was 0 (clear) on the salifert. Nitrates were also 0. But I still had algae.

I then added rowaphos and the algae slowly became less and less. But was still there.

I then added 16 snails and the algae completely disappeared. 16 snails in 25 gallons.

Even on the natural reef, algae will grow. It's just things will eat it to keep it in check.

 

[Rybren]

Thanks Cory.

I do run GFO and Carbon and have a good sized clan-up crew, but maybe it's time to boost its size. Neither the Yellow Tang nor the Coral Beauty are interested in the HA.