Q about light penetration to 'the depths' in aquaria..

[richardsantink]

Hi,

I've got macro algae in a 125g marine tank that seem to flourish at 5" depth, but not to the same extent at 18-20". Would this seemingly minor difference in depth be a factor in the differing growth rates? My Chondrus crispus seems okay at either depth, but Ulva lactuca, seems finicky (which seems odd, given its reputation..) when it comes to depth.

My lighting is in the form of two 36" F30T8 "Natural Daylight" Fluorescent tubes (don't know the actual wattage) placed end-to-end over the tank for 8 hours a day.

Do I need to drag out a Secchi disk and check for water clarity???

Any information, or experiences greatly appreciated..


Cheers,

RAS

 

[Tom Barr]

Not much light it seems to me.
You lack intensity, even if they are 75 w ea, 2x 150w of T8's on a 125 gal tank ain't much to grow anything really, so you get decent algae near the light, but not elsewhere.

Regards,
Tom Barr

 

[PatrikS]

How many watts/gallon would You recommend, Tom, for enough intensity?

 

[Tom Barr]

For what specifically?
Most macros are fine using 4-5w/gal on PC/T5 lighting.
Seagrasses might need more.


Regards,
Tom Barr

 

[PatrikS]

Allright, I see, I was wondering for my macroalgae tank, but after I posted I discovered You have already answered the same question in some other thread. Sorry for asking same thing.

 

[richardsantink]

Hi,

My lighting is in the form of two 36" F30T8 "Natural Daylight" Fluorescent tubes (don't know the actual wattage) placed end-to-end over the tank for 8 hours a day.

Do I need to drag out a Secchi disk and check for water clarity???

Any information, or experiences greatly appreciated..


Cheers,

RAS

As a note, I've since doubled up on my lighting, and now have it growing considerably faster. One thing unusual, is that my Ulva lactuca seems to go through a cycle of growth, then partial die-off which repeats itself. It's as if I'm gaining 20% growth per day, but sustaining 5-10% loss at the same time... ??

RAS

 

[PatrikS]

As a note, I've since doubled up on my lighting, and now have it growing considerably faster. One thing unusual, is that my Ulva lactuca seems to go through a cycle of growth, then partial die-off which repeats itself. It's as if I'm gaining 20% growth per day, but sustaining 5-10% loss at the same time... ??

RAS

I see the same thing on my Caulerpa taxifolia. The old ends get yellowish, then transparent and die off, while the new fronds grow. I read about Caulerpa, and it seems that it is completly natural. But it would be nice if somebody else could comment on our similar experiences.

 

[Tom Barr]

Ulva is a transient weed.
You need to keep the nutrients up there a bit if the tips get decayed etc.
Same with Caulpera.

You should get very healthy full growth.
Both will do better at lower temperatures as well.

Regards,
Tom Barr

 

[PatrikS]

Ulva is a transient weed.
You need to keep the nutrients up there a bit if the tips get decayed etc.
Same with Caulpera.

Regards,
Tom Barr

Dosing for at like 5 ppm KNO3 and 0.2 ppm KH2PO4?

Is it okej to dose TMG for traces?


Thanks a lot!!

 

[Tom Barr]

Yes to all except PO4.
I'd not pulse that unless you have high plant density and then maybe 102x a week.

Regards,
Tom Barr

 

[PatrikS]

Yes to all except PO4.
I'd not pulse that unless you have high plant density and then maybe 102x a week.

Regards,
Tom Barr

Tom, thank You very much, I will avoid dosing PO4. I was a bit concerned about Cu in TMG, that it could kill something due to a lot of scary propaganda about Cu here with lokal reefers. Thanks for clearing out that I can use TMG (2 ml twice a week for my 35 liters tank, sounds good?).

 

[Tom Barr]

Cu, Bleach, medications, heck even salt, it's all about the dose.
Caffine is toxic at high levels, but folks gulp it down every morning.
TMG is not that rich, Flourish is too low in Cu IMO/IME.

You should try dosing 0.2ppm and test how long it takes to be consumed by the tank. Your test kit is only so good at the lower ranges, few can do well at 0.05 ppms or less, they just are not designed ot measure such low levels accurately.
20ppb is about where macroalgae are becoming limiting(that's parts per Billion), most plants, about 50ppb or so. Less than 20ppb : micro algae.
Plants shut down first, followed by macros and followed by micro algae.

Without testig things, it's hard to say and fear is always a favorite, but 3000$ worth of coral you have coddled for 4 years is not something I'd suggest as model to test.

Macro algae and fast growing seaweeds make a better model to explore the interactions. From there, you can go back and see what things might work well and make more predictions on a coral tank.

But....many folks even with low PO4/NO3, huge skimmers, stilll........have their corals die and other issues not related to higher PO4/NO3 and macro algae, so keep that in mind when they bellyache and fear mionger loudly.

There maybe issues with some species, there are always exceptions, but we are after generalizations and patterns.





Regards,
Tom Barr

 

[Tom Barr]

BTW, see the scaper of the month (a neglected part of the site, Greg and I are both grad students studying full time, so we can let things lapse here an there)

It has a lot pics of cold water macros from the nutrient rich deep upwelling along the coast of the Western USA. I've already been very successful with tropical Carribean species and when in Rome, eat pizza.
I live in CA so I use what is around me, the redwood, the rock, the macro algae, the manzanita etc.....
I am keeping them in a 40 gal cube and will get some pics in about 2-3 months.

No one has been successful at artifical media and seagrasses here.
Well, Monterey Bay Aquarium has some seagrass in their kelp tank, but the kelps die fairly quick. They cannot grow the grass anywhere else.
It's due to high wave energy and lots of light for the success in the one spot, the system is all open water so the nutrients and other parameters are all uniform.

Still, if I can identify good horticulture methods, restoration efforts can be used for many of these and better understanding and use in sceince.
Hard to use something you cannot grow in the lab for a test model




Regards,
Tom Barr

 

[PatrikS]

Cu, Bleach, medications, heck even salt, it's all about the dose.
Caffine is toxic at high levels, but folks gulp it down every morning.
TMG is not that rich, Flourish is too low in Cu IMO/IME.

Well, now I can sleep at night, I was really being scared by some reefers saying that - among other things - that TMG and the likes are the sources of all evil.

20ppb is about where macroalgae are becoming limiting(that's parts per Billion), most plants, about 50ppb or so. Less than 20ppb : micro algae.
Plants shut down first, followed by macros and followed by micro algae.

Without testig things, it's hard to say and fear is always a favorite, but 3000$ worth of coral you have coddled for 4 years is not something I'd suggest as model to test.

Macro algae and fast growing seaweeds make a better model to explore the interactions. From there, you can go back and see what things might work well and make more predictions on a coral tank.

But....many folks even with low PO4/NO3, huge skimmers, stilll........have their corals die and other issues not related to higher PO4/NO3 and macro algae, so keep that in mind when they bellyache and fear mionger loudly.

There maybe issues with some species, there are always exceptions, but we are after generalizations and patterns.

Regards,
Tom Barr

This is sooo true, it almost makes me laugh if it haven't been so sad that some ppl refuse to broaden their horizonts, instead of calling names and take one for a fool, when for example I tell them that one can not get rid of microalgae with just limiting PO4. As I understand, the phosphatresins can take level of PO4 down to like 0,20 ppm or something, maybe a bit more. But 0,20 ppm PO4 is not such a big deal for microalgae, they can survive and flourish under less as You say. Instead it's NH4, low O2 levels and jumpy levels of CO2 that are the main source for microalgae booms: it's the first thing one learns with plants, and it must be the same for saltwater. I mean just because you add some salt to water doesnt mean that its a whole new planet.

But limiting PO4 is obviosly a very touchy subject for many reefers. One gets almost accused of heresy for that!

 

[PatrikS]

20ppb is about where macroalgae are becoming limiting(that's parts per Billion), most plants, about 50ppb or so. Less than 20ppb : micro algae.

Btw, Tom, could You give me some sientific reference to this. I know nobody will trust me if I don't give a link or some books name or something to support these numbers. You are not a big authority with the reeffolks.

 

[Tom Barr]

Reef folks are not big authorities with macro algae as it is.........
I get questions all the time about what is it? Why is it growing etc......
They are as clueless as any newbie.

I'm not sure a reference or two is going to convince them or anyone really.
The (Florida) SFWMD did studies on PO4 removal in treatment marine wetlands.
The same applied to the FW systems.
I'm not sure they have published it, but it's available.

They use plants for nutrients removal and sequestrration, which is precisely what folks here do with FW and Marine plants very often.

That does not really matter either, you can find studies that show a clear ecological niche as the size of the autotrophic organism decreases, so does the amount of nutrients required in it's environment.

Do you find small femi plankton in coastal upwelling regions or in the extremely nutrient poor central gyres?

Regards,
Tom Barr

 

[PatrikS]

Yes, Tom, but I cannot exactly explain this thing:

If pest algae can survive under such harsh conditions like above 20 ppb PO4, how would You explain this. A phospate resin can surely not sink PO4 to under 20 ppb PO4. Still several lokal reefers say that all their algea problems almost completly dissapear as soon as they use Rowaphos (a phosphatresin). They ask why does it happen if not for the Rowa limiting phosphate levels?? They see a clear correlation between the use of Rowa and dissapearence of pest algae. How come?

Even if I don't completly beleive them - I have seen several ppls with algae issues in spite of use of rowa - but I still cannot find one perfectly sound explanation.


My speculation is that maybe rowa removes some of the phosphate and in that way evens the relation between the nitrogen and phosphates. Could it be the case?

Or maybe - just a speculation - when they put rowaphos in the sump they get som sort of biological filtration, they get bacteria on the granulates that adds stability.

Or maybe its just cyanobacterias they see when they have more phosphates then nitrates, and when the phosphate levels decline with Rowa the cyano dies back?

Just some wild speculations - I am a bit lost.

 

[Tom Barr]

If pest algae can survive under such harsh conditions like above 20 ppb PO4, how would You explain this. A phospate resin can surely not sink PO4 to under 20 ppb PO4. Still several lokal reefers say that all their algea problems almost completly dissapear as soon as they use Rowaphos (a phosphatresin). They ask why does it happen if not for the Rowa limiting phosphate levels?? They see a clear correlation between the use of Rowa and dissapearence of pest algae. How come?

My speculation is that maybe rowa removes some of the phosphate and in that way evens the relation between the nitrogen and phosphates. Could it be the case?

Perhaps, but not likely, most algae are able to sense when it's a good time to grow or not.

PO4 variation vs a stable level are two different things.
Why doesn't pest algae appear when I add PO4 to my macro tank then?

There's a residual 24/7 yet the pest algae does not grow and they clearly have bioavailable access to all PO4 they could need.

The other issue is what are they testing/how for PO4 measurements.
Most PO4 removers are Iron based.

Or maybe - just a speculation - when they put rowaphos in the sump they get som sort of biological filtration, they get bacteria on the granulates that adds stability.

Could be.
Doubt it though.

Or maybe its just cyanobacterias they see when they have more phosphates then nitrates, and when the phosphate levels decline with Rowa the cyano dies back?

Just some wild speculations - I am a bit lost.

I'll email more later on this one, they saw similar things in FW systems, but the PO4 at higher levels does no harm there, but in the Marine tanks, it can.

There's a narrower range that's optimal.

You should ask those clinging to their hypothesis to explain your observations with PO4.

If what they are saying is true, how can it be there's no pest algae when you add PO4?

Their claim is based that it is causation, yet, you do not see it.

So that hypothesis MUST BE REJECTED and a new alternative hypothesis needs to be offered.

That's the way science works.
Even if it's not all techy, replicates, cool statistics etc and etc, it's stilll basic common sense.




Regards,
Tom Barr

 

[PatrikS]

Tom, thanks a lot for Your reply!

As You say: I dont get algae though my PO4 - in the eyes of most reefers - are high as a house! Besides getting PO4 from fishfood, I dosed just a tiniest little bit of it with KH2PO4, and still no algea. (I'm aware of risk for greenwater if I overdose PO4).

There must be therefore another explanation, but the question is which. It could be that the phosphate resins also remove silicates, and that its the silicates that cause that brown slimy covering ppl take for algae.

Anyway, Thank You very much, Tom for taking time!

----
BTW, I found this, maybe it could be of use to You:

HAB 2000

 

[Tom Barr]

Well, why worry about what the other folks not using macro algae are doing?
I'm not trying to convince them.

Let them think that and then you keep showing them nice examples of macro algae and tell them how you dose to keep them.

Evidence is not going to convince many folks, pictures do a better job.

See my tank here for example:
There is not a single coral in this tank, it's entirely made from macro algae. The damsel I could never catch, I wanted blood shrimps etc, but oh well.

Post or link these pics to them and see what they think

Regards,
Tom Barr