Combating Green Water

[Dan]

Hey guys, do over the past 2 weeks or so I've had a problem with green water.
Tank setup
So set up consists of:
4x2x2 105g Tank
2 large canister filters (1400 and 2000 lph)
2 x Philips 865 39w T5HO
2 X Osram 840 24w T5HO both 8 hour photoperiod
Dose EI starter kit from Aquarium Plant foods uk, and excel or Neuro as carbon source.
50% water change per week.

The tank has been set up for a few months and the dosing etc has been the same for a least 2 of those months.
Over the past few days I've reduced the lighting down to 6.5 hours, and reduced the recommended nutrient dosing by approx 25%. From what I've read a blackout seems a good way to get rid of green water, but I'd rather find another way since I'm growing on Discus and don't want to cover up and not feed for a few days.
Anyone got any suggestions on ways I could tackle this and also what is most likely to be the cause in my set up? (Plants are all still growing as normal)

 

[ceg4048]

UV will clear green water in few days.

Cheers,

 

[Dan]

UV will clear green water in few days.

Cheers,

Forgot all about uv. I had a spare small pond filter with a brand new uv on so I've attached it to the side of the tank and hopefully it should clear up the green water for now.

Are the steps that I've taken the correct ones to stop it coming back? Reading through various algae guides it seems green water is to much nutrients/light/possible sun light.

 

[ceg4048]

Green water has little to do with nutrients but can be triggered by light + ammonia spikes. Sometimes if you play around with the substrate, such as uprooting and moving plants, ammonia will spew out of the substrate. If the rearranging was not immediately followed by a water change this triggers the bloom. I would never recommend to reduce your nutrient dosing, otherwise you could easily trigger some other kind of bloom related to nutrient deficiency.

Cheers,

 

[Dan]

Thanks for the info, I think I've found the problem now. I don't normally notice but since we've been having this cracking weather at around 19:00-21:00 Sunlight manages to shine directly onto the tank through the kitchen window if I leave my middle door open. Given the fact the weather coincides with my problem I'm assuming that is the cause.

 

[ceg4048]

Or it might be a coincidence. Best to look at the other side of the equation.

Cheers,

 

[Dan]

So I've had the UV on for about 5 days now and that combined with a water change has cleared the water up. The slight issue I still have is a green covering at the top of the tank. Difficult to explain so i've attached a pic...


As you can see, main water clear but still this green fog on the top. Is this just the remainder of the green water? and if so will it clear with another few days of UV? Or is it something else?
Thanks
Dan

 

[LancsRick]

Is your pump breaking the surface tension of the surface?

 

[ceg4048]

Might need to add more Excel. It's not economical to do a 100 gallon Excel only tank, but the more plant mass you have the carbon demand also rises.

Cheers,

 

[Dan]

Lancs: Yes the pump breaks the surface, you can sort of see it in the picture at the back. It is quite gentle though.

Ceg: Funny you should say that, I've just ran out of my normal carbon (I use Neuro from aqua essentials) which I dose 15 ML per day. Recommended dosing is 5ml per 250 litres.
So I've just finished mixing up my first bottle of DIY stuff, got my 50% Glut from Bonnymans and mixed 30ml with 970ml of water. Was going to continue with dosing 15ml, as I believe recommended dosing is 1ml per 10 gallon.
Would you suggest I dose more?
Appreciate the help.

 

[ceg4048]

As with gas injection, you'll need to find the happy medium between addressing deficiency and inducing toxicity. The scum indicates the beginnings of either a nutrient or CO2 shortfall (or both). Improve your dosing first to see if that works, and if not then the problem is most likely CO2. Have a thorough read of the thread Surface Film | UK Aquatic Plant Society

Cheers,

 

[ian_m]

I got surface scum couple of weeks after setting up my tank. Soaked it up by floating kitchen towel on surface and using an air stone when CO2 and lights are off. However as CEG says, when things improve/settle down the scum disappears.

 

[Dan]

Thanks for the thread link, one thing though, my surface scum seems to be green and mostly in the thread its talked about a clear scum. Should it just be treat the same?

Regarding the "scum indicates the beginnings of a nutrient or co2 shortfall" that makes perfect sense. I've always slightly under dosed on micro/macro (dosed approx 50ml, instead of the 60-70ml recommended for my tank) because of my heavy stocking. This was probably fine as my plants were taking hold, but now the Rotala and especially the Limnophila have started growing like weeds its makes sense that I should have upped the levels accordingly.
I've upped the dosing to 70ml, and have taken a good netting to the scum so most of it is gone. With this being my first day of dosing DIY glut I'm a little hesitant to go crazy with dosing until I see any negative effects on my fish, so at the moment I'm dosing 15ml per day (I believe the recommended dose would be 10ml). If I see no Ill effects on the fish I may up the dose to 20ml in a week or 2.

Thanks

 

[dw1305]

Hi all,

one thing though, my surface scum seems to be green and mostly in the thread its talked about a clear scum. Should it just be treat the same?

Your surface scum is green because it has a chlorophyll component. Because chlorophyll is degraded pretty quickly when it isn't enclosed in a plant cell (it is a protein), the green colour is caused by floating algae.

This isn't a CO2 issue, the algae have access to aerial levels of CO2 (400 ppm), but it may be the remnants of your "green water" algae trap in the surface layer. Surface scum is primarily composed of water-insoluble organic compounds (proteins, fats, aromatics, etc) from fish food, and/or from the decay of plant and animal matter etc. Because these compounds are both insoluble and lighter than water, they float as a surface layer.

I'd try the paper "towel method" and/or increased surface movement and see what happens.

cheers Darrel

 

[ceg4048]

Darrel,
There is a high probability that the decay of plant matter in that tank is due either to poor nutrition or to poor CO2. Paper towels do not solve the root cause. If you need paper towels to clear the scum then that means you have a bigger problem than you think. Even if you clear it now with paper towels, unless you fix the root cause the problem will return. Chronic marginal levels of nutrients/CO2 in a CO2 enriched tank causes problems, and this is the first sign. As the severity of the deficiency increases so will the symptoms.

I agree that the color of the scum is completely irrelevant. The OP needs to forget about the color because the color depends on what flotsam and jetsam is trapped in the layer.

Cheers,

 

[dw1305]

Hi all,

I agree that the color of the scum is completely irrelevant. The OP needs to forget about the color because the color depends on what flotsam and jetsam is trapped in the layer.

Clive, colour may be irrelevant, but against that it because it is algal it may not be. At this time of year you get a lot of green cyanobacterial scum in eutrophic water bodies.

I've been out a couple of times lately with my "day job" looking at point source pollution events and the changes in the aquatic plant assemblage they cause. We've been trialling tryptophan monitoring sondes (from: RS hydro <Multiparameter Water Quality Sondes & CTD s>) as an alternative to BOD testing, and they look really promising. I can't go into all the details, but this paper, gives the back-ground: "Can fluorescence spectrometry be used as a surrogate for the Biochemical Oxygen Demand (BOD) test in water quality assessment? An example from South West England" < Can fluorescence spectrometry be used as a surrogate for the Biochemical Oxygen Demand (BOD) test in water quality assessment? An example from South West England >.

I'll pass on the health of the plants, but if the scum returns, and remains green, it is caused by surface floating algal cells. If it returns, but not as a green scum, its colour relates to the "flotsam and jetsam" trapped in it.

If you need paper towels to clear the scum then that means you have a bigger problem than you think. Even if you clear it now with paper towels, unless you fix the root cause the problem will return. Chronic marginal levels of nutrients/CO2 in a CO2 enriched tank causes problems, and this is the first sign. As the severity of the deficiency increases so will the symptoms.

I'm not recommending paper towels, or UV, as a long term fix. I virtually never have any surface scum on any of the tanks, possibly because I like to have a lot of gas exchange surface, so run a venturi or have an elevated spray bar which breaks the water surface.

The main thing for me is that my tanks, in your terms, all receive too much PAR, don't have any added CO2, have huge plant loads and are chronically nutrient depleted, but I don't have any scum. I have some "biofilm", but not very much, and I don't have algal out-breaks.

cheers Darrel

 

[ceg4048]

Well, the thing is that if the OP's tank has algae and excessive scum then they are both part of a wider fault of malnutrition, which will be either nutrient or CO2 related. Every tank has biofilm layers, and that's normal. The surface agitation and gas exchange techniques works in your non-CO2 tank simply because you are importing the gases into the tank. The mass you have accumulated is a CO2 and Oxygen "sink".

Also, I doubt the claim that the tank receives too much PAR. From the photos you have shown and according to your propensity to use duckweed which covers the surface (I made the assumption that all your tanks use this) the PAR penetration is reduced. If you are using Tungsten lighting then the PAR levels output by the bulbs may not be as high as you think.

Is your CO2 really that low? What's happening in the substrate? If you have a near zero maintenance program then there is a high probability that the sediment is high in organic content accumulation, will be high in bacterial action (presumably aerobic) which means a higher bacterial respiration and CO2 generation. Are the plants in the tank root CO2 feeders? Possibly. Cryts, swords and other "rooty" plants typically can take advantage of sediment CO2 more so than less "rooty" plants.

Is the sediment nutrient depleted? Hardly. Again, there ought to be plenty of nutrition in the sediment from feeding and fish waste if this is low maintenance.

Have the plants had the stability and time to adjust their physiology to a lower nutrient and CO2 environment? Yes, most certainly. Chlorophyll density and Rubisco density should have been optimized over time.

So, I've made these assumptions about your tank, and these factors easily explain why a non-enriched tank, with minimal inorganic nutrient supplementation is problem free. We can see this time and time again. But your tank isn't this tank. One cannot easily compare the two tanks because of the fundamental differences. Also, there are plenty of non-enriched tanks that have severe cases of surface scum and it's precisely because of environment conditions in those tanks that are less optimized than in your tank. What we know about CO2 enriched tanks is that their their physiology changes because of the addition of fuel, but that their fuel usage rate is disproportionately high, so they run out of fuel more easily than in non-enriched tanks, but even so, non-enriched tanks are not immune to energy shortfalls either. That's why the same problems can occur in both types of tanks., and why both types of tanks can also be problem free. The fundamental reasons are the same, but the mechanisms are different.

Even if the OP solves the immediate problem with UV, paper towels, skimmers and so forth, that will change nothing. The problems will simply become more acute and a few months from now the tank will suffer more problems if root cause of energy depletion is not addressed.

Cheers,

 

[dw1305]

Hi all,

So, I've made these assumptions about your tank, and these factors easily explain why a non-enriched tank, with minimal inorganic nutrient supplementation is problem free. We can see this time and time again. But your tank isn't this tank. One cannot easily compare the two tanks because of the fundamental differences. Also, there are plenty of non-enriched tanks that have severe cases of surface scum and it's precisely because of environment conditions in those tanks that are less optimized than in your tank.

I think the assumptions are probably mainly correct, I'm not sure about the light because I don't have a PAR meter. However the lab tanks are in windows (N. facing) so they will be getting a large amount of additional daylight. My lighting is all T5's at the moment, although I have had the tanks under 400W SON T grow-lamps producing about 10,000 lux of light at tank level, albeit when they were final stage of the waste water processing, so they would have elevated levels of nutrients.

I think the OP intends to remain high tech., so it will be interesting to see what happens. Personally I'd recommend a much greater plant mass, including the infamous floaters.

cheers Darrel

 

[Dan]

Appreciate all the responses even if some have slightly baffled me lol.

As I mentioned I've physically removed most the scum and green water has cleared, I've also adjusted my dosing/lighting (70ml per day using Aquarium plant food uk ei kit/ 15ml DIY glut per day/ 7 hour photo period). I do approx 60% water change weekly due to do growing Discus and feeding beefheart.

I'm also quite happy to increase plant mass if you think that may help. Was looking for some nice tall stem plants since I doubt the Echinoduros or going to get as tall as I would like. So I can move them a little forward and a nice tall easy growing stem plant to cover the back (was thinking Gymnocoronis Spilanthoides).

 

[sciencefiction]

I do approx 60% water change weekly due to do growing Discus and feeding beefheart.

That's probably where the problem with green water came from initially. There's possibly higher amounts of ammonia that the tank deals with due to the heavy high protein feeding, combined with higher light it creates green water algae and surface scam. The surface scam is something the filter and UV haven't been able to deal with because it wasn't mixed in with the water column. You may want some decent surface movement despite CO2 injection, because you may need higher amounts of oxygen, thus growing enough aerobic beneficial bacteria to deal with the ammonia that gets produced. Hence why people don't grow discus in planted tanks.