Algae problems in low light non co2 tank

My low light tank had been running for about six weeks now and i'm sad to see that some algae has apeared, lets see if we can work towards a solution...first ill supply you all with general info about the tank.

Tank size: 11 gallon (10.5gallon/40liter netto)

light: 11 watt pl lamp

Filter: Eheim 2213 / Outlet = original eheim, inlet = aquaticmagic lily pipe.

Substrate: Sand

Flora: Bolbitis heudelotii and microsorum pteropus narrow atached to spiderwood, Sagittaria subulata, Rotala sp green.
+ some Camomba and Heteranthera zosterifolia in a pot to help cycle the tank.

Fauna: 9x Boraras brigittae, 2x Boraras maculatas, 6x Caridina Multidentata


Nutriënts/care

Water change: Once a month 25%. Top offs with regular tap water when needed.

Micro's: Profito, once a week

Macro's: Was told that i did not need to add macro's but for the first 5 weeks or so i only had 2 fish so added some in case.

Added around 8 ppm NO3 and 0.5ppm PO4 last week, did the same this week because the nitrate tested below 5ppm. I have no way to test PO4 but am saving up for a Hanna photometer.

Also added some easy carbo for the last 10 days, this was to combat some BBA, im happy to say this worked as after 9 days i was able to scrape of the now slimy BBA easily.

I do have a little surface scum, lily pipe is raised for a little ripple but that does not remove it entirely.

As soon as i spotted the algae (3 days ago) on the leaves i covered up the reflector of my lamp with black, should probably have done this from the start, the light is now noticeably less

The story is getting way to long but i hope atleast its clear..if you have any questions please ask them, i will post pics of the tank and algae
today.


The first 3 pictures are from 4 weeks ago and some things have changed in the tank.

View attachment 4456 View attachment 4458 View attachment 4457

 

Fts
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Rotala sp. Green changing from emersed to submersed, doing fine i think.
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Sagittaria subulata doing ok.
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GDA be damned
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Finaly the algae the whole post is about, i have almost zero experience with algae (not complaining) so i have no idea what kind it is and what to do with/against it. I just try to keep the plants growing and this time since i did not want to use CO2 i tried to keep the nutrient demands low by using low light.
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What am i missing or doing wrong here? Any advice is more than welcome.

 

I'll read those sites/articles today, thank you.

Yes i read about the GDA and the 6 hour photoperiod thats seemed to reduce it. 6 hours is just way to short for me to enjoy the tank but its still very usefull information and research.

I've recently covered my reflector so i hope that that will help a bit. Should have done this from the start but focused on other things in and around the tank and forgot about it..

I thought about the waterchanges and have no problem with doing more of them but after reading about the co2 fluctuations this brings with it i became a bit worried about them.

 

This is what im talking about:

(Quote from Tom Barr)

Changing CO2 around day to day, hour to hour, week to week the plant struggles and spends more energy adapting to CO2, than with growth, acquiring nutrients, catching light etc. In non CO2 systems, changing water frequently causes a spike in high CO2 week to week etc, done only once every few months is better.