FAQs on Controlling Genus
Halimeda Marine Green Algae
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"Algae"/(Cyanobacteria), Diatoms, Brown
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Marine Aquarium Algae Control
by Robert (Bob) Fenner
Early Autumn for Halimeda?
I have been very happy with a Halimeda macro algae I got over a month ago. Yet I
have noticed over the last week it is turning a “golden” color on some of the
“leaves”. These leaves also seem to be affected by specs of coralline algae and
look a bit furry as well.
<I see this in your excellent pic>
I take it that there isn’t really an Autumn season for Halimeda in the ocean
lol—what’s it doing?
<Mmm; appears to be "suffering" from a lack in water quality and/or being
outcompeted given present conditions. What re your Ca, Mg in particular? Water
I have this feeling this older part of the Halimeda is possibly not doing well.
I’m by far a reef expert like you all, but I do know some plants try to produce
offspring quickly when they aren’t doing so well.
<Agreed; and likely relevant... the month of your having this algae... takes a
while for it to adjust or show signs of not doing so>
In the last week I’ve seen multiple sprouts coming out of the rock frag this
Halimeda is on. Should I clip off the older plant or maybe just the affected
<I'd leave all... the calcium et al. in the existing thalli/pads will add to the
I have read they do not like being pruned though...or should I wait for the
little ones to grow a bit bigger first?
Inserted a pic below. Any feedback is appreciated as usual.
-LED 89w par intensity up to 700, lights on for 7 hours
-2 returns @ 266 gal each
-1k icecap gyre at 700 gph peak
<These are certainly fine, in fact, a bit high. I'd allow the [Ca] to drop to
about 400 ppm, the [Mg] to about three times Ca>
-Test bi weekly with Salifert & dose Seachem reef builder, calcium, & magnesium.
-10% weekly water change with Red Sea
-I only feed frozen twice a week (half cube typically) with a small broadcast of
zooplankton (1-2ml), pellets 4 days, and no food on water change day.
-skim aggressively with a Aquamaxx HOB 1.5
<What is the temperature here? I'd keep in the upper 70's F max; and do you have
measurable phosphate? Necessary. Bob Fenner>
Re: Early Autumn for Halimeda?
Just tested my phosphates and nitrates too just in case. Phosphates are
undetectable and so are nitrates.
<... mate; all life we're interested in need both. This IS the likely cause
of failing health here>
It’s summer here in Florida, so my tank peaks at 84F and averages 82F during
the day at the moment. I don’t have a chiller so the best I can do is run
lights at night and at that time lower the a/c.
<I would cut the lights back, scoot the top/cover a smidgen>
Last week I did remove my chemical filtrants because I felt it was making my
water “too clean”—possibly too soon to really make a solid judgment but from
this base test, it may show I was right. I reduced my weekly water changes
to 10% from 25% as well.
I do have other macros in the tank including: Codium, shaving brush, blue
Ochtodes, Caulerpa prolifera, Padina, an unidentifiable Rhodophyte, and
dragon’s breath—all of which are flourishing.
<Ahh; well, these may well be outcompeting your new/er Halimeda. B>
"Adversity is merely fuel for virtue~"
<Not necessarily, or always>
Re: Early Autumn for Halimeda?
Good evening Bob!
<Good morrow Danila>
Well, after listing and realizing how many macros I own, I had a feeling
you’d say it was possibly being outcompeted. So ironic—for months I was
battling nitrates and phosphates and now I’m one of those looking for them,
Well, do you think it wise to wait a week, or few perhaps, to see how the
lack of chemical filtrants and reduced % of water changes impacts the tank?
<Yes; this is a sensible approach>
I’ve done further research on Halimeda so I know what it looks like when
it’s about to explode spores...appears white and with green fuzzies.
I’m not sure my nano tank would handle the ammonia that can build up after
they go sexual?
<Mmm; not much ammonia/protein involved here. Likely if your system is
fine/balanced, you have sufficient filtration, circulation, and likely
"caught" the event early on you'd be fine>
I feel I am dancing on a fine line the way it looks. Today it actually looks
a bit better and the babies are growing like Aiptasia went out of style.
If I still have zip phosphates and nitrates after observing, I’d like to
maybe switch to biweekly, or less maybe, water changes before trying to dose
stuff just to raise nutrients.
<Mmm; well; I wouldn't purposely "add nutrient/s", but maybe feed your
livestock a bit more>
As always, appreciate you and your team’s advice. You all have been helping
me since I started with a 45g that ran with a penguin filter (LOL!) over 10
<Glad to find you have stuck with the hobby. Can be trying at times eh? Bob
What to do about the moss/algae
This is a pic looking down over my 29 BioCube. Can you identify my
bright green leafy plant?
I like it and my little gumdrop gobies love to hide in it. Can I prune
it back a bit?
<If you like.>
And I have developed an overgrowth of moss/algae.
<Looks like a Derbesia sp. Commonly referred to as hair algae.>
Not sure why or how. I'm scrubbing it off weekly and pulling it out in
tufts. Are my lights bad?
<Spectrum shifts in old bulbs can contribute to growth.>
Everything was moving along fine till about 2 months or so ago. Now I
have this miss everywhere. My parameters are right where they should be,
<Likely due to the algae consuming excess nutrients.>
so all I can think is it has to do with my stock light in the BioCube.
(I've only had the tank for about a year, and it was new when purchased)
<T5s generally need to be replaced every twelve months. Halides every
I have Chaeto in the back, and I also use a small phosphate filter in
the middle chamber. So, I'm not sure what causing the moss.
<Excess nutrients and possibly spectrum shift from old bulbs.>
Should I go to my LFS and get a few snails? Turbo?
<Pinpoint what is fueling the algae and remedy. Adding a predator is
simply a band-aid.>
Thanks for any help you can provide.
<Quite welcome, Jordan>
Halimeda propagation... From the mouths, keying of...
Dear Bob/Crew Member
I would like to spread Halimeda algae throughout my system.
Could I take a few coins, pulverise it in a blender (in tank water), and
then re-add it to the system?
<Mmm, better to simply "hand-break" apart and spread segments where you
want them... need to assure steady, high presence of ALL biomineral (Ca,
Mg) in proportion (about 1:3) ALONG with alkalinity>
I am thinking about dieback, then re-appearance in strange locations in
the tank, how does it do this?
<Systema naturae... conditions that favour it, exclude others>
Special cells or ones that modify on coming into contact with a
<What a great question... I don't know; but I suspect you have a
doctoral thesis and more going here>
Please tell me if this is a mad idea, and if there's a better way to do
<Not mad; and as above>
I have read and often hear that Halimeda takes a lot of the nutrients
from the tank. Other than Phosphates, Nitrates, and Calcium what other
nutrients does it take from the water?
<Some Magnesium of elements hobbyists have test ability for... Other
than these, other less to trace materials can be supplied through water
changes, feeding of other livestock. Bob Fenner>
Just a quick question today:
I've got a huge amount of Halimeda exploding in my tank (yeah, in
the display, I don't have a sump, and I kind of like the way it
looks). I have to cut it back weekly. I've let it grow out a bit,
though as I'm thinking of taking some to offer at my local reef
club. So I'm wondering how best to move it? Can a simple cutting
"take root" (or whatever they do), or should I pull bits out
from the rock?
<Both can work... some times becomes quite invasive...>
Then obviously transport in a bag in water, but what would the
recipient do with it? Just add it to their tank or sump, or do they
have to attach it somehow?
<Can attach with a bit of epoxy, reef "glue", or just bury
in substrate, place in cracks in the rock>
<Welcome. Bob Fenner>
Hello, My name is Luke and I own a 220 reef. My problem is my Halimeda,
the stuff is starting to take over, <Typical... but good in a way
(for nutrient export). Just be sure it's not sucking down your
calcium levels.> everything I have read has said that it should not
do that, its a solid root plant. <Hmm... do you not read WWM? Or
even Wikipedia? Halimeda is not a plant. It is an algae. Please see
http://en.wikipedia.org/wiki/Halimeda> I think it might be the fact
that I have a very large number of corals so I cant get down to the
roots, and that might be what is causing the spread. My question is how
do I kill it, without killing or slowing growth of my other corals,
lots of SPS. <You might just have to do your best to keep manually
removing it. I don't see any other way to kill it without risking
your corals. But I wouldn't get too down about it... having it grow
so well, and continually removing it is great for nutrient export.>
Thank you so much, Luke Hines <De nada, Sara M.>
Halimeda Removal 7/12/04 I have a 90 gallon predominantly SPS
tank. The tank is infested with Halimeda and I'm VERY
tired of manually removing it. The even bigger problem is
its growth is interfering with frags for space and its demolishing my
calcium levels. I use a calcium reactor and my tank seems to
be the ideal breeding ground for this algae. Is there
anything that might eat it? Any suggestions? <heavily
calcareous algae like Halimeda are generally unpalatable to most
herbivores. I cannot think of any reliably reef-safe grazers for you.
You are remitted to manual extraction. Be prepared to do a hearty water
change right after to remove it all by hand... try to cut it down to
the rocks or gently chisel it off (use a sharp chisel to wiggle and
scrape it off clean). Avoid tearing the "leaves" up much for
fear of noxious exudations (low risk) to the corals> I probably
remove a 2 quart container per month of the stuff. Matt
<no easy solution here Matt... just make sure you don't
contaminate your tank with fresh deodorant for how deep your arms will
be in the aquarium <G>. Best of luck, Anthony>
New Print and
eBook on Amazon
Marine Aquarium Algae Control
by Robert (Bob) Fenner