# Increase phosphates to combat GDA



## andusbeckus (7 Feb 2020)

It has been suggested to me that increasing phosphates will help with eliminating the GDA I currently have. 

I use a premixed dry fertiliser that I just mix with water so can increase phosphates alone. Will just an increase in everything have the same affect or would I need to increase just phosphates in relation to everything else?


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## andusbeckus (7 Feb 2020)




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## Geoffrey Rea (7 Feb 2020)

Hi @andusbeckus

Could you provide more details; how old the scape is, Co2 management, lighting period, light intensity, which dry fertiliser you use, water change amount per week?

As in other threads a full front shot of the tank and equipment gives others a good idea of how you’re running things.

Have heard of increasing phosphate levels to tackle green spot algae but not green dust algae. Plants look healthy in the background, have you tried cleaning your rocks with a wire brush before water change and making it a big water change?


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## andusbeckus (8 Feb 2020)

Scape is roughly 3 months since filled and 2-3 month dry start before that. Lights (Chihiros A601) on 100% but raised fairly high so roughly equivalent to 50% at normal height. 3pm - 10pm fading on and off over a 30min period. Co2 is lime green although I did have a day or two without optimum levels a few weeks ago due to introducing fish. Fertiliser is this one https://www.co2supermarket.co.uk/aq...all-in-one-complete-fertiliser-mix-gsc35.html I have used this in all my scapes for the last 3 years and although have the odd tiny bit of algae nothing like this. 

I have scrubbed it off clean twice and has come back so would really like to get to the root of the problem. Snails are keeping things cleaner but not ideal.


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## Zeus. (8 Feb 2020)

You do have quite a large surface of rocks exposed to light so aglae on them is to be expected, some amanos or more snails may would help too.

As a side note your carpet of MC/HC is looking like it would benefit from a trim as its getting quite think- if left too get too thick the lower parts die of and then it starts to lift up


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## andusbeckus (8 Feb 2020)

Yeah I’ve trimmed back since the photo was a week or two overdue. I am getting some more Bucephalandra to cover some of the rocks but I always wonder how Iwagumi scapes with exposed rocks keep it away.


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## Zeus. (8 Feb 2020)

andusbeckus said:


> Yeah I’ve trimmed back since the photo was a week or two overdue.



  just thought it was worth a mention  



andusbeckus said:


> I always wonder how Iwagumi scapes with exposed rocks keep it away.



Think they tend to be short term scapes due to the high maintenance require to keep them looking good hence they class them as 'Hard to do' or 'for the experienced scaper'



andusbeckus said:


> I am getting some more Bucephalandra to cover some of the rocks



Remember Buc. isn't keen on high light levels


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## Siege (8 Feb 2020)

Get a small wire tooth brush type tool on the rocks, followed by a massive water change.

you can drain the water and paint/spray the stones with liquid carbon or 6%hydrogen peroxide. Just watch the fish.

nerite snails will help.


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## andusbeckus (8 Feb 2020)

Siege said:


> Get a small wire tooth brush type tool on the rocks, followed by a massive water change.
> 
> you can drain the water and paint/spray the stones with liquid carbon or 6%hydrogen peroxide. Just watch the fish.
> 
> nerite snails will help.



Done all of that and have Nerites in there but it won’t fix the cause. It just comes back again.


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## Geoffrey Rea (9 Feb 2020)

Buckle in, long reply....



andusbeckus said:


> Done all of that and have Nerites in there but it won’t fix the cause. It just comes back again.



Have had a few iwagumi’s with the same issue, healthy plant growth/rocks coated.

Here’s some of the attributes I’ve found correlate with cleaner rocks:

- As age of scape gets greater, the frequency of GDA/GSA/Diatoms on rocks gets less. (Estimate this is due to more well established plant mass, leaner soil with age so more use of water column available nutrients and larger bacterial colonies due to high saturated o2 levels in matured planted tanks)

- The lower the amount of light intensity, the slower the growth of algae on your rocks (but slower growth of your plants too so... system wide consequences)

- The more nerites you have, the less of a problem this becomes (as it is a good food source but you’ll need a lot of them)

The above seems obvious but in a well established tank growth controlled by light intensity slows growth of algae, with the ‘right’ amount of nerites in balance with this then they rid most of the algae on the rocks by eating it = gives the impression you have relatively clean rocks. You then have turned the problem into a controlled food source. Remaining issue is you’ve used light to achieve this, something that affects everything else in the system which could be counterproductive depending on your goals.

(NB I would reduce the light ramp up/down time to 15 minutes or less)

This all assumes perfect Co2 and maintenance as well.

Dosing glutaraldehyde on the regular and especially after a water change will go a long way towards killing remaining algae spores in the water column after a water change if you’re not already utilising this.

Phosphates... if anything I’ve found an excess of phosphate, at certain points in a scapes life, to exacerbate these issues. Others will disagree and roll their eyes and shout the mantra, “ferts don’t cause algae!” and in general I agree. However, my experience says adequate fertilisation doesn’t cause algae, but ignoring how ratios affect uptake is a little short sighted and outside how I interpret EI dosing.

For example EI dosing:

NO3 20ppm, K 30ppm, PO4 3ppm, Mg 10ppm per week.

Other ratios that I would advised in tandem with above rates to generate good growth conditions in high tech:

Ca:Mg - 4:1 – 3:1 and K:Mg - 3:1 – 2:1

Just as a side thought. Will increased phosphate affect your iron availability? Will this cause further issues? There is instances where I’ve found upping nutrients can stall problems e.g. upping nitrate to slow the spread of BGA. So not dismissing the suggestion you were given, just encouraging some thought regarding unforeseen consequences to upping phosphate without good reason.

Maybe you can elaborate on why upping phosphate was suggested?

Thinking of what you want to achieve though, clean rocks.

These are the less pragmatic solutions:

- You can design your scape so you can regularly remove rocks and paint them with glute, rinse and return.

- You can cover rock surfaces in sensible plants that you can readily trim e.g. Pinnatifida, Tripartita etc

- You can have more than one tank with nerites in. If rocks get covered deploy all your nerites in that tank for the day then remove (a biological solution)



andusbeckus said:


> It just comes back again.



The backwards assumption to this is you can stick a rock under high light in an established aquarium and expect nothing to grow on it. All tanks have algae but the aquarist can create solutions to manage it.

Hope something in all this may help, sorry it’s long winded but ultimately you’ll know what will work for you. Just throwing some thoughts out there.

There’s always James’ Planted Tanks for info as well:

http://www.theplantedtank.co.uk/algae.htm


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