Green Water

Themuleous

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Hi All,

Ive got a very stubborn case on green water in my 20g. Ive run the UV steriliser several times over the last few months and it has cleared but it always comes back. Anyone got any tips?

I have reduced the lighting to 9hrs (2x18w freshwaters) would it be an idea to reduce this to 8hrs? Also I'm reduce PO4 to 1ppm 3x per week as I was dosing 1.5ppm 3x per week.

Thanks all :)

Sam
 

milla

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Leeds
Sam

Does the tank get direct sunlight ?

I had the same problem with a tank. Tried everything uv, Water changes every 3 days. No joy always came back. No other algae issues but green water. Turned out that the tank was getting direct sunlight from the window, Moved tank and problem solved.

Andrew
 

ceg4048

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Themuleous said:
Hi All,

Ive got a very stubborn case on green water in my 20g. Ive run the UV steriliser several times over the last few months and it has cleared but it always comes back. Anyone got any tips?

I have reduced the lighting to 9hrs (2x18w freshwaters) would it be an idea to reduce this to 8hrs? Also I'm reduce PO4 to 1ppm 3x per week as I was dosing 1.5ppm 3x per week.

Thanks all :)

Sam
Hi Sam,
Sorry if I sound like a broken record but PO4 doesn't cause algae, ammonia does. :idea:
The reason that it returns is because of ammonia generation in the tank. Ammonia is being generated, possibly due to fish load and or inefficient filtration, but more likely because the plants are ill due to some form of starvation. Let's review compulsory dosing:

Gandalf's magic calculator says that a 20G ought to get the following:

3/16 teaspoon KNO3 3X per week
1/16 teaspoon KH2PO4 3X per week
Possibly 1/2 teaspoon MgSo4 3X per week (or pinch of GH booster once a week) depending on Mg available in tap.
1/16 tsp CSM+B (or 4 ml TMG) 3X per week
CO2 :?:...

These numbers can easily be doubled if you have high plant mass and/or high light. Is that 36 watts of T5 or is that T8? If that's T5 then it's quite a bit of light as the wpg rule breaks down at lower volumes. 9 hours is fine I reckon, but do the UV to get rid of it, water changes etc etc etc and rigidly maintain dosing.

We really need to break ourselves of the habit of suspending dosing when we get an algae outbreak. On the contrary when an outbreak occurs it's usually a signal that we ought to increase dosing.

Also, what is your filtration and how often do you clean the filter? Detritus buildup in the filter breaks down and produces ammonia.

Cheers,
 

Ray

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At the risk of putting the cat amonst the pigeons, I read in a JBL lighting handout that the reason direct light causes a problem is because your plants have adapted to the wavelengths of light available from your tubes. The sunlight comes and of course the agae can react quicker to exploit the new wavelengths available... JBL marketing team, of course, implied this to justiied buying thier lights because they are similar to sunlight and so your plants will already be adapted to those wavelength, solving the problem.

I suspect there is some truth in this, if your tank gets natural light (or even, for short periods, sunglight) daily I don't think this is an issue so long as you adjust your WPG accordingly.

So in summary, as Clive suggests, ammonia sounds most likely?
 

Themuleous

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Aston, Oxfordshire
A few things re the tank, the lighting is T8 and the tank has been running for over two years. I did recently started EI and the plants have been growing great in the lower light with EI. Fish stocking hasn't changed. The filter is an eheim 2222, cleaned monthly, that's what Ive always done. The green water started for no obvious reason, that's whats confusing me :wideyed:

I'm careful with the water changes not to disturb the substrate. There is a bit of mulm on top of the substrate though, which is impossible to get out due to the plants.

Sunlight isn't an issue, is doesn't get any direct or reflected light.

Ceg - I hear your point, but I cant figure out where NH3 might have come from.

Thanks for all the advice.

Sam
 

ceg4048

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Sam,
A long shot but how is your CO2? Also how much of everything are you dosing? I'm just searching under every stone here so bear with me; If you pre mix with water how are you preparing the mixture (just to check, you might have miscalculated the concentration mixture)?

If there are no dead fish unaccounted for, no excess mulm in either tank or filter and no over-bright lights then the ammonia has got to be coming from the plants. Nitrate and CO2 are linked in such a way that an increased uptake in one causes an increased uptake demand in the other. Nitrate and phosphate are linked in a similar manner. I reconsidered your proposal to reduce the phosphate dosing and I now think it can help since it would reduce the nitrate demand. Typically a better option though would be to increase the nitrate.

Also you stated that the tank was fine for years and the green water occurred some time after starting EI. How were you dosing before? Did you go from no CO2 and no dosing to CO2 plus EI?

Cheers,
 

Themuleous

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Aston, Oxfordshire
CO2 is fine, nice green drop checker :)

I cant remember how I worked out the stock solutions, but I used Chucks calculator. Trace mix is as per AE website, although I am double dosing as I had an iron deficiency.

No dead fish other than the odd one, but I'm pretty sure this is old age as Ive had some of them a fair few years now.

Before I wasn't dosing at all, nothing, no ferts or co2, a bit of trace when I remembered. I reckon much of the problems are to do with the CO2 addition, as once I added that the plants even pearled at the end of the day, which they never did before. I think the tank is still trying to stabilise following the CO2 addition and the consequential increased demand on ferts.

Thanks for your help

Sam
 
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