# What would trigger algae to grow on glass?



## anewbie (1 Oct 2021)

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:


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## ceg4048 (1 Oct 2021)

anewbie said:


> 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,


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## anewbie (1 Oct 2021)

ceg4048 said:


> 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.
> ...


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.


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## tiger15 (1 Oct 2021)

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.


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## anewbie (2 Oct 2021)

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.


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## plantnoobdude (2 Oct 2021)

anewbie said:


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


kh2po4, monopottasium phosphate.


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## MichaelJ (2 Oct 2021)

anewbie said:


> 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


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## anewbie (2 Oct 2021)

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


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## MichaelJ (2 Oct 2021)

anewbie said:


> -
> 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.



anewbie said:


> -
> 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


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## John q (2 Oct 2021)

anewbie said:


> What exactly causes algae to form on glass and leaves


To much light in a nutshell.


anewbie said:


> 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.


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## MichaelJ (2 Oct 2021)

John q said:


> To much light in a nutshell.


Yes.


John q said:


> 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


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## John q (2 Oct 2021)

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.


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## MichaelJ (2 Oct 2021)

John q said:


> 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 😂


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## anewbie (2 Oct 2021)

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 ?
-
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.


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## MichaelJ (2 Oct 2021)

anewbie said:


> 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.



anewbie said:


> 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


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## anewbie (2 Oct 2021)

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 ?


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## plantnoobdude (2 Oct 2021)

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.



anewbie said:


> 1810 mg per 40 gallon


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


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## anewbie (2 Oct 2021)

I can up co2 a little as well as 


plantnoobdude said:


> 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.
> 
> ...


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.


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## plantnoobdude (2 Oct 2021)

anewbie said:


> 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?


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## plantnoobdude (2 Oct 2021)

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.


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## anewbie (2 Oct 2021)

I might get some sachem liquid phosphorous to see if it does any good and then consider ordering the solid. Ebay only has it from international shippers.


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## Driftless (2 Oct 2021)

How often do you clean/scape the inside glass of your aquarium?  Cleaning/scraping right before a water change will help keep the algae at bay.


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## anewbie (3 Oct 2021)

Driftless said:


> How often do you clean/scape the inside glass of your aquarium?  Cleaning/scraping right before a water change will help keep the algae at bay.


I do it on demand; until recently once every 2 or 3 months. The past 2 months; once every 2 or 3 weeks. I do water changes reliably once a week. The aquarium has been set up for 18 months.


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## Driftless (3 Oct 2021)

anewbie said:


> I do it on demand; until recently once every 2 or 3 months. The past 2 months; once every 2 or 3 weeks. I do water changes reliably once a week. The aquarium has been set up for 18 months.


I have settled on doing my tanks' glass every other week.  I find, for me, that interval keeps the glass looking clear and I think that waiting longer than this interval allows the algae to get started and for spores to be floating around your aquarium.  I don't need to see algae before I clean glass.


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## MichaelJ (3 Oct 2021)

anewbie said:


> 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 ?


Hi @anewbie  Buy this NilocG Monopotassium Phosphate. 1 lbs is $5 +Tax + Shipping. When you do your next 50% WC in your 40 US gallon tank (which is 20 US Gallon) you add 1 gram (1000 mg) which is a quarter (1/4th) of a US Teaspoon. With consecutive 50% water changes It will slowly build up your tank to about 9ppm of PO4 minus the plant uptake. That's it - plenty of PO4. Nothing to worry about with regards to Phosphate... and you can take that out of the equation. If in doubt you can always invoke the almightly @Zeus. He is the Fertilizer Meister around here, and will strike down with all his might and tell you exactly the dosing you need 

Cheers,
Michael


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## Zeus. (3 Oct 2021)

@anewbie what fertiliser are you using ATM ? or what DIY mix yields are you dosing?


ceg4048 said:


> There is a greater than 90% chance that the cause is poor CO2 at that location.



Which could be flow/tank turnover related, Flow is *King* of the CO2 injected tank and CO2 issues are often resolved by addressing better flow first, your tank from the pics does seem to have a low surface agitation. What's the output of your filter and any power heads?
When was the last time you cleaned your filter and what media do you have in it ? . In my 500l tank I use to clean the filter media weekly and it always needed it ( I was using the filter as a detritus trap when weekly turkey blasting the carpet)


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## anewbie (3 Oct 2021)

Zeus. said:


> @anewbie what fertiliser are you using ATM ? or what DIY mix yields are you dosing?
> 
> 
> Which could be flow/tank turnover related, Flow is *King* of the CO2 injected tank and CO2 issues are often resolved by addressing better flow first, your tank from the pics does seem to have a low surface agitation. What's the output of your filter and any power heads?
> When was the last time you cleaned your filter and what media do you have in it ? . In my 500l tank I use to clean the filter media weekly and it always needed it ( I was using the filter as a detritus trap when weekly turkey blasting the carpet)


Actually the tank has fairly high flow; more so than my other aquariums. The back has a large jet stream (run via air) on the matten filter; the front has 2 small submersed pumps one on either side. You can see one of the pumps in the 2nd picture; the jetstream and back current is hidden by the plants but the surface agitation is high. There are a few dead spots on the middle side where the young guppies hang out but those areas are not algae problematic.
--
The front flow extends fairly deep into the aquarium (I can tell when i drop pellets); the back flow I'm not sure is that deep but i've never really checked. However you raise a good point. I'm trying to decide if the algae started when i increased as the pumps are relatively new addition the flow and maybe the flow is causing the algae issue (of course this would be inverse of what you said but still there might be a relationship).
--
All the filtration are sponges and i last clean them about 3 weeks ago. They normally get clean about once every 6 to 8 months. I can watch the flow through the matten filter fairly easy by seeing the water level on the opposite side and when it shows signs of clogging i clean it.


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## anewbie (3 Oct 2021)

Ok. I order some phosphate; i was griping earlier that shipping was 2x the cost of the actual mineral but i tossed in some root tabs as i'm running low (i hate their root tabs since they float but whatever). It'll take a week for it to arrive and another 3 weeks to see if it helps so in 4 to 6 weeks i'll update this thread with this experiment. After it arrives I'll look into increase the co2 a touch. I mostly do it by ph drop with the absolute max of 1 (I do have a drop checker to safety check). The issue is that this is a fish tank with plants and i worry about the fish well being with all these chemicals and co2 (reduce oxygen).


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## anewbie (5 Oct 2021)

Zeus. said:


> @anewbie what fertiliser are you using ATM ? or what DIY mix yields are you dosing?


I dose thrive+ once a week 4 pumps.


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## Zeus. (5 Oct 2021)

anewbie said:


> I dose thrive+ once a week 4 pumps.


So




 for your 40gallon you will be dosing 7.5ppm NO3, 5ppm K, 1.3ppm PO4 and 0.4ppm Fe which is a tad on the lean side IMO.
two or three times a week would be better IMO ( or at least try for 6 weeks)
x3 a week yields ( allow so slight difference as we used UK gallons so will be slightly more in US gallons)


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## anewbie (5 Oct 2021)

I'm sorry i add additional iron - 4 pumps of nilocg iron at the same time as thrive+ so there is a bit more iron. The reason I don't dose more often is i want to keep the nitrate level below 40ppm. I will add more po4 starting next week if the shipment arrives in time. I'm not sure if that will be sufficient or not. It might be that the issue is not related to po4 at all. Fe and PO4 and NO3 will be covered starting next week; I guess there is some Ca in the water (my water is kh 3 gh 7).  I also put in root tabs every 3ish months. I am very concern about the total die-back of the crypt in the back. That really seems like a rejection of the tank by a 2 year old plant - maybe an issue with organics building up in the substrate ?
-
This is what the tank looks like as of this morning the real concern are the complete death of the crypts in the back and the repens in the front beginning to show severe degradation: I hope it isn't an issue with the substrate because it would be a nightmare to tear down and replace;  The rotala at the top is doing pretty well; I just trimmed it extremely heavily the past two weeks.


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## eminor (11 Oct 2021)

i took the light pill, i'm now a low/medium light guy, it was a hard time in my brain


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## foxfish (11 Oct 2021)

You mention something about an air stream and now I see two pumps facing each other.
Can you explain a bit more about the flow and flow rate?


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## anewbie (12 Oct 2021)

foxfish said:


> You mention something about an air stream and now I see two pumps facing each other.
> Can you explain a bit more about the flow and flow rate?


I'm not sure how to quantify the actual flow of the back jetstream. If you look at the back right corner you will see a matten filter; the primary flow comes from that jetstream which is air driven.  In the picture the edge of the matten filter sponge is visible at the very top of the back right corner. The two pumps on the side are small (80gph) and turned down a bit so it doesnt' blow the kubotai around - i would guess each is running around 40 gph; but the actual stream from them is narrow and does not extend to the bottom of the aquarium. I thought about trying t make a spray bar out of some air tubing but i don't think it would work well. I do have a pair of wave makers and originally i put one on the side midway down but at 250gph it was too strong.


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## foxfish (13 Oct 2021)

Well generally speaking we would not recommend setting up opposing power heads but offer all of the flow in one direction.
I think you could improve the flow pattern considerably by moving both the power heads to one side and not having whatever you have at the back.


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## anewbie (13 Oct 2021)

foxfish said:


> Well generally speaking we would not recommend setting up opposing power heads but offer all of the flow in one direction.
> I think you could improve the flow pattern considerably by moving both the power heads to one side and not having whatever you have at the back.


Well the suggestion that i 'get rid of that thing in the back'; suggest you are not familiar with matten filters; so that will have to remain. I could move one of the pumps to the other side and lower it but is this a good idea?

Also since I upped the co2 the algae seems less pronounce and more important the repens in front have started to out grow the algae on them. Tuesday i added the additional phosphate and reduce the amount of thrive+ by 50% but it is too early to see if it will be beneficial.


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## foxfish (13 Oct 2021)

Well that is good news if things are improving 

I think a matten filters is a type of air powered sponge filter?

 Flow is a very much discussed subject on this forum and is critically important if you want to get the best out of your C02 injected planted tank.
I am sure there are many ways to achieve great flow but a very popular method is based around a slow overall movement within the tank and into the plant mass.

For instance if we use a spray bar, the flow would push along the surface layer and then be pushed down the front glass. 
At this stage he flow is no longer jetting but is a smooth water movement heading toward the back of the tank and in amongst the plants.
Now we hope this will be a continuous movement, a circular motion going around and around as a mass of water.

If you point two pump at each other then the result will  be chaotic and non repeating, the result won’t offer the same effect as a consistent flow coving the whole tank but…. It may just work for you but, it  is not a popular method.

Anyway if things are going your way there may not be any need to change things further.


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## anewbie (23 Nov 2021)

It has been about 6 weeks and things have improved quite a bit - i did three things - added phosphate; increased co2 and increase light by reducing the ha'ra rotala that was floating and suffocating everythng. I can't say for sure which had the largest effect though I'm leaning towards increasing co2 and adding more phosphate.


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## anewbie (3 Dec 2021)

So things are not perfect; I'm now beginning to get some clumps of bba; vaguely I think i read somewhere the too much phosphate will encourage bba; so I will reduce the phosphate to 1/8-1/16 of tbs to see if that helps over the next 8 to 12 weeks.


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