What is this brown, flowing algae?

Welcomed to APC! I have had similar looking algae blobs in my tank, but I have never known exactly what form of algae it is. I think you need to remove all of the blobs that you can, and probably reduce the light intensity. Those two plants don't require high light.

If you nitrates are at zero you may be encouraging the algae by starving the plants. What substrate do you have? Do you dose any fertilizers? Do you use CO2?

I just have two of these over the plants for 6 hours per day: NICREW ClassicLED Plus Planted Aquarium Light, Full Spectrum LED Fish Tank Light for Freshwater Plants, 12 to 18 Inch, 8 Watts https://www.amazon.com/dp/B07LH2FJNC/ref=cm_sw_r_cp_api_i_3ZplEb7EH3N9E

The substrate is pool filter sand. You can actually check out my build here: https://www.capitalcichlids.org/forums/threads/setting-up-my-135g-with-sump.36809/

I dont think its a cyanobacteria. Maybe some type of Chrysophyta or Diatom?

Amiga276 said:

I have the same question....What is this stuff? I have had the same brown flowing algae in my tank for some time and it has been very persistent. I have been troubleshooting ferts, & CO2 thinking its lighting intensity problem but I think I am at the upper limit of how much fert and CO2 I can put in the tank before killing live stock.

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What lighting do you have, and what are the tank dimensions? Algae love lots of light.

hoppycalif said:

What lighting do you have, and what are the tank dimensions? Algae love lots of light.

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It's a 30 watt LED. 60 cm in length. Sorry that's all the specs I have on the light. 8hrs a days. Considering reducing to 6hrs per day

Tank:
Width: 60cm (23.62")
Height: 36cm (14.17")
Depth: 30cm (11.81")
tank's volume is 64.8 liters/17.1 U.S. gallons.

Given that the height of the tank is only about 14 inches, it is unlikely that you need more light, but you could easily have too much light. You could test that by putting a layer of fiberglass window screen between the light and the tank. That cuts the intensity almost in half. If you had too much light you should see a result by cutting it nearly in half.

hoppycalif said:

Given that the height of the tank is only about 14 inches, it is unlikely that you need more light, but you could easily have too much light. You could test that by putting a layer of fiberglass window screen between the light and the tank. That cuts the intensity almost in half. If you had too much light you should see a result by cutting it nearly in half.

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Thanks hoppycalif. The light is currently hanging about 6 inches above the water but I could raise another ~ 5 or so inches.

Would reducing duration have a similar impact to algae growth as reducing intensity?

I can't remember anyone experimenting to see if lighting duration can substitute for lighting intensity. Intuitively it seems unlikely.

One reason I like the window screen method for reducing intensity is that it can be relied on for dropping the intensity by 40%, assuming you use gray fiberglass insect screen.

Photosynthetic Photon Flux Density (PPFD). PPFD is normally measured using mol m−2s−1

Second is in the measurement. So time (duration) is part of the equation.