Weird results, any insights appreciated

[shai]

I have started a waterfall scrubber almost 3 months with some weird results. Very little dark green algae forms on the sheet but a lot of GHA forms at the bottom of the acrylic enclosure which I clean out every 2 weeks.

The tank is a RSM 500, no room in sump so I am using a relatively powerful (I think) pump Jebao dcs 2000 rated at 2000 L/hr to almost full to feed the ATS which is located outside the sump on a stand. I feed one and half cube a day .
The ATS is from ebay and has cheap LED strips on both sides . The screen is 30.5cm by 14 cm. The light cycle is 18 on 6 off. I am still carbon dosing and using GFO but the algae that used to form in the tank is much reduced.

I was thinking about upgrading the LEDS when I noticed the GHA forming at the bottom. Can anyone knowledgeable point me to what I might be doing wrong. The drainage as you can see in the pic is not the best which may explain why algae is forming at the bottom but why is it not forming on the screen, is my flow too slow .. since the pump does have to push the water a fair distance up. The last image shows the water flow, I am happy to take one without the lights if that helps

[SantaMonica]

Welcome from Australia,

The light is just too strong, compared to the amount of nutrients in the water, and the limited growth on the screen to absorb the light. The reason for growth at the bottom is the strong air/water turbulent interface there, which is how Upflow scrubbers work, and also because the light is dimmer there.

If you reduce the dosing and the GFO, it will help. Also can try to shade the light with a cloth, or use just 1 light instead of 2 (I think you have 2) until it starts growing.

[shai]

Cheers mate. That is a very interesting theory, always thought these LEDs were no good. Anyways will stop the GFO and carbon dosing and run one light for 2 weeks and report back. Thanks for your input

[shai]

Ok been a while. I think I have tried everything. On the flow side I tried max flow and reduced flow. With the former nothing was growing on the side where the water entered the screen so I reduced it to 50% now I have growth all over. I ran light from 9 hours a day to 19 hours a day , no change. All I am still getting is the dark green growth which I have been getting from week 1.

I have stopped carbon dosing and the phosphate reactor media has not been changed in 2 months so it is ineffective. The protein skimmer is still on but is skimming very little to nothing. The tank is 1.5 year old and is generally healthy.

I can see some hair algae on the wavemaker and dark green carpet on the back wall. I have ordered decent lights for a DIY fixture but I do not think that is the issue. Logically I should have some growth even with weak lights. The only other reason is the water quality but I feed 1 cube a day with 1/4 Nori sheet and therte is no external filtration except for the skimmer which is really not doing much. Other thing is signs of algae in the tank so I am stumped.

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Hair algae on flow maker

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Green algae on the back wall
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[SantaMonica]

What is phosphate, and have you measured silicates? Do you know the TDS of your top-off water?

[shai]

What is phosphate, and have you measured silicates? Do you know the TDS of your top-off water?

Phosphate is .07, TDS is 057 . I cant measure silicates but I do not have any cyano in the tank. I am guessing this colour of algae grows on fresh water setups, thats why you are asking about TDS and silica? I changed the DI resin in November but the 2 stage filters are due for replacement.

The TDS is quite high, I have changed the sediment and carbon filters as well after reading your reply :-D . I will report back but if I am barking up the wrong tree please do feel to add

[Marksfish]

Silly question, but has the screen been roughened?

[SantaMonica]

Need to get TDS fixed first, to 002 or 001 or best 000

If excess silicates are there, it can allow bright green diatoms to form, which don't get thick, and don't hold on well... they just wash off.

[shai]

Ok TDS is down to 0 now. Will take some time through the auto top off.. might do a 20% water change . Will let you know of the results. I will hold of on upgrading the lights till I find out what the issue is . @Marksfish Yeah mate rough as guts