What would trigger algae to grow on glass?

[anewbie]

What exactly causes algae to form on glass and leaves. I have a hi-tech 40B that has been setup for over a year; and recently more algae has started forming on the glass and I'm not sure what is triggering this behavior.

I do 50% water changes once a week; the only change I've made is adjust the light so it was slightly less intense and slightly increase of the blue spectrum (about 15% less bright and the blue spectrum ended up rising about 15% relative to the previous setting; this happen because instead of using a profile i set it to 6500K (previously it was too red).

I have also noticed a bit of die back in some plants - the ones under the canopy of rotala make sense since they are not getting enough light but some of the ones in front that have plenty of light are also not doing as well which makes me think something is out of whack.

This is a bit of an older picture by about 3 weeks; the crypt that was quite huge in the back center has shows severe reduction making a hollow point behind the pinto anubia in the middle - a picture won't really show it very well since it is dark down there. I had assumed this was due to being light starved but I'm not sure that is the cause any longer. Also the mini-AR in the middle front will send out shoots that will grow very well and then a couple of weeks later they stop growing; the leaves develop strong algae and it sends out a new healthy shoot. Somehow this doesn't seem normal for mini AR. Shouldn't the shoot stay in good condition longer ?


here is a picture taken this morning (this morning i removed a bunch of the rotala so light can reach the back center to see if the crypt would regrow - it used to be a huge plant that was 10-12 inches high - and 6-8 inches wide:

 

[ceg4048]

What exactly causes algae to form on glass and leaves. I have a hi-tech 40B that has been setup for over a year; and recently more algae has started forming on the glass and I'm not sure what is triggering this behavior.

Hello,
Algae in planted tanks is always caused by too much light and either not enough nutrition or not enough CO2. The typical algae on glass is Green Spot Algae (GSA) which appears, as the name implies as groups green spots. Algae forms on hardscape because it is easier for them to attach to non-growing surfaces. Plants resist/evade this by growing, thereby presenting a moving surface. Other tactics are used, but essentially hardscap surfaces stays put allowing the algae to grab a hold.

If the algae on you glass in GSA then this is an indication that you have any combination of poor CO2 and poor PO4 for the given light intensity.
Unless a PAR meter is used the human eye is not really able to determine what is bright. This seems counter-intuitive, but the human visual cortex is not very sensitive to blue or red, but is very sensitive to green and yellow. Plants are mostly sensitive to blue and red but do use other colours. So they see the world completely differently than we do. Although you may have lowered the intensity, by increasing the blue it my have been that the PAR actually increased. This is not a certainty but it is a possibility.

When plants die back, it is rare that the cause is lack of light. There is a greater than 90% chance that the cause is poor CO2 at that location.

Cheers,

 

[anewbie]

Hello,


When plants die back, it is rare that the cause is lack of light. There is a greater than 90% chance that the cause is poor CO2 at that location.

Cheers,

I have a par meter and can get some par readings tomorrow if that help. The crypt is right next to CO2 injection; so while there might not be enough co2; it would not be the crypt that has lack of access. it is possible that nutrients are low as I've been a bit stingy with adding thrive+ due to higher than desired nitrate.

The crypt die back is very troublesome to me if it is not due to lack of light. I'll post some par readings tomorrow afternoon after the light reaches full intensity (it has a 1.5 hour ramp up); on the surface it sounds like the easiest solution is to reduce the intensity of the light - is that what you are recommending?

Also can you think of any other reasons why the crypt would have died back - the plant was quite huge before I added co2 which was last Dec (i had the plant for 18 months without co2) - about 30 months ago i set up a 20 long and after a year i broke it down and transfer everything into the 40b. Then 6 months after i setup the 40B (christmas) I added co2 which was 8 months ago.

 

[tiger15]

Common algae on the glass are GSA and GDA. Many sucker mouth algae eaters will clear GDA off glass, but only Nirite snail will. GSA is the worse of too and once established, you have to scrape it off with a razor Blake. High light and low phosphate will cause GSA, so it’s best to prevent it from starting. Lower light on the glass by using directional LEDs, and a horde of sucker mouth acan help reduce GSA from starting. Even without algae, bio slime will grow on glass so it is always helpful to have sucker to keep glass clean.

 

[anewbie]

The aquarium has oto (9), bn (2) and some babies, and mystery snails. There is no slime I've seen so I guess this is GSA? It scrapes off with very little effort with a blade or finger nail. Does this suggest I should add PO4 if so is there a good way to add it without nitrate. Changing the light is not an option; but i can change settings on it or swap it with a fluval 3.0 which i ahve in the closet.

 

[plantnoobdude]

PO4 if so is there a good way to add it without nitrate

kh2po4, monopottasium phosphate.

 

[MichaelJ]

I've been a bit stingy with adding thrive+ due to higher than desired nitrate.

Hi @anewbie I would not worry about intentional high levels of NO3 (Nitrates) through dosing in a planted tank, unless close to toxic level (say if your tap water is already extremely high on Nitrate or the tank is really polluted). Following El dosing you will routinely add 25-30 ppm of NO3 weekly and will only benefit plants and suppress algae.
As for GSA, if you want to suppress GSA I'd say go high on KH2PO4... aim for 10ppm of PO4 - worked for me - never seen GSA in any of my tanks since I started high levels of Phosphates - and I used to struggle with GSA on my Anubias and other slow growers all the time back in the day. However, if you light intensity is not met by available CO2 or maintenance (WC's) is insufficient you are likely still going to struggle with algae regardless of your NPK dosing. Provided that maintenance is up to snuff, the one-two punch is to go abundant on macro nutrients (NPK) and lower the light intensity (not necessarily the hours).

Cheers,
Michael

 

[anewbie]

Ok here are some par readings:
Just below the water under the light it is around 350
I couldn't get a good reading at the bottom below the light due to most of it being heavily shaded but i did get one reading that was over 100.
Just below the water at the front of the tank it is around 230
At the bottom of the tank in front it is around 80 (no shade but not directly below the light)
where the crypt is even after removing some rotala it is around 10
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My concern with nitrate was that at times it is getting above 40; i do a 50-60% water change once a week; right now it is around 15 but i did 2 water changes this week (something I will not be able to normally do).
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Do you still think the issue is that I need to add more phosphate?

 

[MichaelJ]

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My concern with nitrate was that at times it is getting above 40; i do a 50-60% water change once a week; right now it is around 15 but i did 2 water changes this week (something I will not be able to normally do).

How much do you dose? How do you measure? Nitrate can be hard to measure. In addition, some NO3 test kits such as the API kit is all over the place. It's almost impossible to get a consistent reading and if so, tell if you got 20, 40 or 80 ppm... (the patches for 40 ppm and 80 ppm are virtually indistinguishable). So, the best way to go about it, in my opinion, is to look at the water report, know how much you dose weekly and be vigilant with maintenance which it appears that you are) so you don't get unchecked buildup from waste. In that way should be able to deduce your approximate amount of NO3. And as long plants look and grow well you know your levels are good.

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Do you still think the issue is that I need to add more phosphate?

Adding more PO4 will help on the GSA situation. Your not getting enough PO4 with thrive+ only... if you just follow the instructions you only get a measly (3 x 0.4 ppm) 1.2 ppm per week.

Of course, all this have to be combined with proper application of CO2 (Dosing of the CO2, flow/circulation etc.) as pointed out by @ceg4048.

Cheers,
Michael

 

[John q]

What exactly causes algae to form on glass and leaves

To much light in a nutshell.

around 230
At the bottom of the tank in front it is around 80 (no shade but not directly below the light)
where the crypt is even after removing some rotala it is around 10

That's enough light to sustain a cryptocoryne, if its struggling then the usual suspect would be lack of co2 and or nutrients.

No idea if 10ppm of phosphate will allow you to blast the tanks with light and not get gsa, I can however say 'half confidently" that lowering the light intensity a tad will probably reduce the amount of gsa you have in the tank.

 

[MichaelJ]

To much light in a nutshell.

Yes.

No idea if 10ppm of phosphate will allow you blast the tanks with light and not get gsa, I can however say 'half confidently" that lowering the light intensity a tad will probably reduce the amount of gsa you have in the tank.

Hi @John q As I see it, the phosphate level is just piece of the puzzle. Low phosphate levels definitely encourage GSA - but its hard to say what's enough... hence the fairly arbitrary 10 ppm... it needs to be combined with lowering the light intensity - the one-two punch I was referring to above, and fixing/improving the CO2 situation.

Cheers,
Michael

 

[John q]

Not disagreeing with you Michael, phosphate may or may not be the solution to this particular puzzle but suspect good old klingon light levels are the cause.

 

[MichaelJ]

Not disagreeing with you Michael, phosphate may or may not be the solution to this particular puzzle but suspect good old klingon light levels are the cause.

Yep. Its a distinct possibility, that moderating those Klingon photon torpedo launchers alone will clear the sector from unwanted intruders 😂

 

[anewbie]

Is KH2PO4 the only way to add phosphate - not finding it on amazon; nilogc has it but shipping is 2x the cost of the mineral.

Is that 10ppm per what unit - 10ppm per 40 gallons; 10ppm per gallon - 10 ppm per liter ?

Just how low should i make the light - isn't 8-10 par pretty low ?
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The algae is new the light was reduced before the algae started showing up (i had it higher); isn't it odd the algae started after i lowered the light or maybe the issue is the rotala is sucking out all the phosphate as that has been growing out of control.

 

[MichaelJ]

Is KH2PO4 the only way to add phosphate - not finding it on amazon; nilogc has it but shipping is 2x the cost of the mineral.

Potassium phosphate K3PO4 would work as well (I have never used it myself - as I get potassium from other sources). Adding 1 gram to 100 Liter would yield ~4.5 ppm of PO4.

Is that 10ppm per what unit - 10ppm per 40 gallons; 10ppm per gallon - 10 ppm per liter ?

parts per million is equivalent to milligrams per Liter ... so 10 ppm is 10 mg/l. (for all practical purposes in our hobby at least).

Cheers,
Michael

 

[anewbie]

So I would need around 1810 mg per 40 gallon. Seems like a lot. How do you get your phosphate? I could use sachem potassium but that isn't phosphate ?

 

[plantnoobdude]

I dose 5ppm po4 upped from 3ppm and it seems to have improved a decent amount.
i don't think the issue is light, 80-90 par is quite conservative
I personally think it's poor po4 levels coupled with poor co2.

1810 mg per 40 gallon

is not a lot. mg is milligrams. 1/1000th of a gram
that is 1.81g.

 

[anewbie]

I can up co2 a little as well as

I dose 5ppm po4 upped from 3ppm and it seems to have improved a decent amount.
i don't think the issue is light, 80-90 par is quite conservative
I personally think it's poor po4 levels coupled with poor co2.


is not a lot. mg is milligrams. 1/1000th of a gram
that is 1.81g.

And what product do you use to add phosphate? I can certainly up the co2 a bit but it has been stable during both the period of no algae and algae; I'd like to up the phosphate first.

 

[plantnoobdude]

I can up co2 a little as well as

And what product do you use to add phosphate? I can certainly up the co2 a bit but it has been stable during both the period of no algae and algae; I'd like to up the phosphate first.

i use monopottasium phosphate.
perhaps ebay has some for sale?

 

[plantnoobdude]

also. dry dosing really is the best option for high tech tanks of large size. getting the full kit from nilocg may be worth it.