Why does hair algae sometimes outcompete macroalgae?

[Randy Holmes-Farley Verified Community Expert]

Why does an algae scrubber with hair algae outcompete hair algae in the display? Is it absorbing trace elements that the hair algae in the display need?

IF it does that, then yes, it is competing for a chemical of some sort. Might be N, P, trace elements such as iron or manganese, etc.

 

[djf91]

I also have a lot of buildup of what PaulB refers to as “mulm”. Which according to others seems to be a build up of sparse filamentous algae holding detritus in between it. I’m assuming low flow is the cause of this.

During my scrubbing last night, I tooth brushed off a piece of some Acropora encrustation that hadn’t been looking good the last couple of weeks and also had GHA and mulm right against it. The coral growth seemed very brittle. I think it’s been said by some here before that these patches of mulm and GHA create localized low ph zones on the substrate underneath where they grow. Seems very useful in destroying calcareous coral and calcareous algae (corraline) growth.

 

[Dan_P]

@Dan_P @taricha
What do you think is going on by scrubbing the algae off the rocks? Am I irritating it enough and these algae don’t like physical disturbance? Am I allowing for bacteria/ corraline to move in and take over?

Why does an algae scrubber with hair algae outcompete hair algae in the display? Is it absorbing trace elements that the hair algae in the display need?

Scrubbing algae from the rocks likely destroys the roots/holdfast. It simply cannot sprout again. Also, when a surface is disturbed by scrubbing, it is recolonized and it might be that the hair algae reproductive cells cannot colonize this spot.

I don’t know that an algae scrubber outcompetes display tank algae. That concept might be rational but it might not be the complete explanation.

 

[OhioReefKeeper]

I have been battling gha for 3 months now it’s on the back glass and all rock work. I go in and pull as much as I can and it seems to grow back faster. I have a lot of hermit crabs and snails a sea hare and a urchin the urchin is the only thing that puts a noticeable dent in the gha.

 

[djf91]

I have been battling gha for 3 months now it’s on the back glass and all rock work. I go in and pull as much as I can and it seems to grow back faster. I have a lot of hermit crabs and snails a sea hare and a urchin the urchin is the only thing that puts a noticeable dent in the gha.

How’s your alkalinity?

I’m starting to think my GHA issue re-emerged when my alkalinity went from 8.6 to 7.7 over the course of a month. I think this caused all my new corraline growth on rocks to die off thus fueling GHA and also giving up prime real estate to the GHA. This is my theory at least. I’m now slowly bringing alkalinity back up to 9.

I think in newer systems and even 1 year old systems started with dry rock, the ecosystem is very fragile. A change in water chemistry or a major disturbance can open back up the door to nuisance occupiers.

 

[TokenReefer]

Try a BIG turbo snail. I can attest my big snail did work on this rock overnight. This was long bushy GHA and the rock was absolutely covered with it. Pushed the zoa frag off too...

The next night it cleaned the rest of the rock...

 

[OhioReefKeeper]

How’s your alkalinity?

I’m starting to think my GHA issue re-emerged when my alkalinity went from 8.6 to 7.7 over the course of a month. I think this caused all my new corraline growth on rocks to die off thus fueling GHA and also giving up prime real estate to the GHA. This is my theory at least. I’m now slowly bringing alkalinity back up to 9.

I think in newer systems and even 1 year old systems started with dry rock, the ecosystem is very fragile. A change in water chemistry or a major disturbance can open back up the door to nuisance occupiers.

You are very right about new systems with dry rock it takes time for the biome to build up on the rocks to help. And thanks for the alkalinity idea going to try that.

 

[92Miata]

How’s your alkalinity?

I’m starting to think my GHA issue re-emerged when my alkalinity went from 8.6 to 7.7 over the course of a month. I think this caused all my new corraline growth on rocks to die off thus fueling GHA and also giving up prime real estate to the GHA. This is my theory at least. I’m now slowly bringing alkalinity back up to 9.

I think in newer systems and even 1 year old systems started with dry rock, the ecosystem is very fragile. A change in water chemistry or a major disturbance can open back up the door to nuisance occupiers.

A drop from 8.6 to 7.7 over the course of a month shouldn't bother anything. 7.7 is a very normal reef alkalinity.

That being said - yes, coralline will absolutely compete with GHA and kill some of it off - (as will corals, etc) - so you're probably right in the loss of coralline being the driver. Having a "mature" reef is largely about having enough surface competition that there's no space and no opportunity for nuisance algaes to get a foothold.

When you add a piece of dry rock to a mature reef - you'll get a burst of film algae on it, usually followed by GHA. You can then watch the coralline (etc) get a foothold and burn its way across the rock. Similar to watching an acro grow across coralline - there will be a thin bare gap where war is being waged.

(and yes, sometimes the GHA wins those individual wars - but that's usually because the coral isn't healthy/growing. GHA flare ups are usually preceded by some sort of growth affecting event)