Macroalgae stopped growing and cyano bloomed

[Dag]

Why does each algae seem to have its time?

At one time bubble algae flourished in my tank. No more.

At one time halimeda flourished in my tank. No more.

At one caulerpa flourished in my refugium. No more.

Now cyanobacteria holds the stage. I trust this too shall pass.

No major changes in the last several months, except a switch to Oceanic salt.

 

[sjvl51]

Cyano usually is a sign of low flow and high nutrients. Maybe try to increase your flow in the areas that cyano is showing up. A 25 to 30% water change or two will help reduce the nutrients.

Vickie

 

[Dag]

I have high flow. And the tank was up for over a year with no cyano. Lights were changed. If there are high nutrients, why isn't the macroalage growing?

 

[sjvl51]

That could be because the cyano is using the nutrients first. If the macroalgae has slowed down growing, it is not removing the nutrients as fast as it used to allowing something else to use them - like cyano.

One reason that your macroalgae has slowed down its growth could be a lack of iron. http://www.advancedaquarist.com/issues/aug2002/chem.htm
"The benefit of iron appears to be at least two-fold (and maybe three-fold). The main benefit is that at least some species of macroalgae grow faster, and appear a darker, more attractive green, when the tank is dosed with iron. In addition to the aesthetic benefits, this increased growth permits the macroalgae to be a better nutrient export system. A secondary benefit is that faster growing macroalgae may better compete with microalgae, which is often a source of frustration to reefkeepers. One more speculative benefit is that it may decrease the likelihood of caulerpa undergoing sexual reproduction, creating water quality problems."

Is the cyano growing in certain spots or all over? I know that it will first show up in areas that don't have as high a flow due to rocks, etc. I then remove as much as possible and adjust the powerheads to increase the flow in that area.

Vickie

 

[kmk2307]

Aryeh,

I think the answer is succession driven by changes in nutrients. The concentration of phosphates (PO4) in your water has probably increased. Halimedia can't calcify when lots of phosphates are present. Caulerpa likes some phosphates but gets outcompeted by cyanobacteria when there is a lot of PO4 available. Unfortunately, cyanobacteria are about the most efficient primary producer there is in a PO4 rich medium. Do you use purified water (like RO) for water changes and top off? Do you test the nutrient concentrations in your water?

Kevin

 

[Dag]

Yes, I use RO/DI.

I never had a phosphate problem before, and I was using Rowaphos anyway.

How do you test for nutirient concentrations?

Vickie, the cyano started in the fuge, which was a lower flow area and then migrated to the main tank, which is high flow.

 

[kmk2307]

Aryeh,

You can use a phosphate test kit to see if you have free phosphates in your tank. You may also want to test for nitrates though that is probably not the problem. I like Salifert test kits.

Kevin

 

[romunov]

How much do you skim?

 

[Dag]

I skim wet. Nothing changed in my husbandry. cyano just blossomed after 1 1/2 years with no problem.

 

[kmk2307]

Negatively charged phosphate molecules tend to stick to sand and rock. Once the rock and sand are saturated, cyanobacteria blooms can appear rather suddenly.

Kevin

 

[Dag]

Saturated after a year and a half?

If so, is there any cure short of dumping all the rock and sand?

 

[kmk2307]

I would run phosphate remover and blast the refugium with light to try to get caulerpa or chaetomorpha to grow.

 

[Dag]

I was running phosban. Refugium does have light.

Won't the cyano eventually use up the phospate sticking to the rocks and sand, and then go away?

 

[Plantbrain]

Has the temp changed?
Ca++ levels or Alk?
Fe?

Check those first.

If those are in good shape, check the NO3 level.

I have never found any correlation when other nutrients are non limiting with PO4 and cyano with marine plants. Diatoms, but never Cyano.

Marine plants such as Caulerpa require far more nutrients to grow well than Cyano's.

So I would say that is it a lack, rather than an excess, I've seen many folk's crash and melt their Caulperas and it was due to a lack of NO3 and nutrient supply after their plant biomass became large if they had good, Ca/Alk, Fe.

Careful not to confound your notions about what causes what.

You can remove most of the Cyano now, water change etc.

Unless you plan on runnign a tank at less than 10ppb, yes biliion, you are going to have very rough time truely limiting algae, fish food, plant leakage etc, the cyano's can get the PO4 before it has a chance to run into the water column and get bound by the PO4 remover.
None of you have tracer stable isotope mass spects and I highly doubt you have any kit that is accurate at the 10ppb range to 50% or more, even I don't and I have access to the state's research lab.

It also runs in the face of using marine plants to begin with.
They are the exporters, we don't need PO4 removers, that's the plant's job.

They should export plenty of PO4 on their own.

I would bet you are removing way too much nutrients that the marine plants would be using and leaving stunted plants as a result since you are using a skimmer.

You could add some KNO3 and see.

I've added KNO3 to my marine planted tanks for a couple of years with excellent results.

I would add more plants and less PO4 remover, cannot do too much with PO4 remover, you can feed fish and sell the plants, they also look nicer.

Regards,
Tom Barr