Dr Mike Oxgreen
Member
I am in the process of restarting my 20 litre nano tank, and I’m getting persistent oily surface scum that comes back within 24 hours after being mopped up with kitchen paper. It’s slightly iridescent, and doesn’t break up when I dip my finger into it.
Taking into account Clive’s advice elsewhere that this is usually due to plant stress caused by excess light, or insufficient nutrients or CO₂ I have been dialling back my lighting intensity and period - but I’m unsure how far I should go. I believe I’m already dosing nutrients generously, and my CO₂ drop checker is a light green at the start of the lighting period, going yellowy-green towards the end - so I know I’ll have to reduce my bubble rate slightly when I add fish.
Let me give you the tank details...
Tank: 40 x 25 x 25 cm
Light: 1200 lumen Beamswork LED plus 800 lumen Interpet LED (but see note below)
Filtration: Eheim classic 2211 external, ceramic balls plus Purigen
CO₂: Sodastream, 1.5 BPS, in-line diffuser
Fert: TNC complete, 1ml per day (triple dosage to approximate EI)
Substrate: Tropica soil powder and JBL Proscape Plantsoil
Plants: Rotala walichii, Hottonia palustris, Cryptocoryne wendtii “green”, Lilaeopsis novae-zealandiae, Anubias nana “bonsai”, Eliocharis acicularis “mini”, HC “Cuba”.
Fish / shrimp: none yet, waiting for cycle
Water: KH 4°, GH 7°, pH 6.5 approx, temp 24°C, TDS 175-225, NH₃/NH₄⁺: 1-3 ppm, NO₂⁻: 0, NO₃⁻: 20-40 ppm.
Note: I’m well aware that the lights give way more power than I need, and I don’t intend to run them anywhere near capacity. I use an LED controller that allows the intensity to be varied. The reason for having two light units is to give a more even spread.
The tank has been running for about three weeks, and I planted it about 10 days ago. I’m dosing Dr Tim’s ammonium chloride and waiting for the cycle. Ammonia goes down slightly, I assume because the plants are using it. I have no significant algae yet, apart from an incredibly faint dusting on the front glass.
I am currently running the lights at 30% (i.e. 600 lumen) with a period of 6 hours, of which the first and last 15 minutes are ramping up and down. CO₂ comes on about three hours before the lights and goes off about 90 minutes before the lights.
So as I say, I’m still getting the oily scum each day. Interestingly, the Rotala seems to be saying “that’s it, I’ve had enough” and starts closing its leaves at least an hour before the lights go off. Does this indicate that I should shorten the period? This plant is still in very juvenile form, although it has grown at least an inch from the tissue culture in the last 10 days.
Am I worrying too much about the scum, or does it indicate that the balance is wrong?
Many thanks for your advice!
Taking into account Clive’s advice elsewhere that this is usually due to plant stress caused by excess light, or insufficient nutrients or CO₂ I have been dialling back my lighting intensity and period - but I’m unsure how far I should go. I believe I’m already dosing nutrients generously, and my CO₂ drop checker is a light green at the start of the lighting period, going yellowy-green towards the end - so I know I’ll have to reduce my bubble rate slightly when I add fish.
Let me give you the tank details...
Tank: 40 x 25 x 25 cm
Light: 1200 lumen Beamswork LED plus 800 lumen Interpet LED (but see note below)
Filtration: Eheim classic 2211 external, ceramic balls plus Purigen
CO₂: Sodastream, 1.5 BPS, in-line diffuser
Fert: TNC complete, 1ml per day (triple dosage to approximate EI)
Substrate: Tropica soil powder and JBL Proscape Plantsoil
Plants: Rotala walichii, Hottonia palustris, Cryptocoryne wendtii “green”, Lilaeopsis novae-zealandiae, Anubias nana “bonsai”, Eliocharis acicularis “mini”, HC “Cuba”.
Fish / shrimp: none yet, waiting for cycle
Water: KH 4°, GH 7°, pH 6.5 approx, temp 24°C, TDS 175-225, NH₃/NH₄⁺: 1-3 ppm, NO₂⁻: 0, NO₃⁻: 20-40 ppm.
Note: I’m well aware that the lights give way more power than I need, and I don’t intend to run them anywhere near capacity. I use an LED controller that allows the intensity to be varied. The reason for having two light units is to give a more even spread.
The tank has been running for about three weeks, and I planted it about 10 days ago. I’m dosing Dr Tim’s ammonium chloride and waiting for the cycle. Ammonia goes down slightly, I assume because the plants are using it. I have no significant algae yet, apart from an incredibly faint dusting on the front glass.
I am currently running the lights at 30% (i.e. 600 lumen) with a period of 6 hours, of which the first and last 15 minutes are ramping up and down. CO₂ comes on about three hours before the lights and goes off about 90 minutes before the lights.
So as I say, I’m still getting the oily scum each day. Interestingly, the Rotala seems to be saying “that’s it, I’ve had enough” and starts closing its leaves at least an hour before the lights go off. Does this indicate that I should shorten the period? This plant is still in very juvenile form, although it has grown at least an inch from the tissue culture in the last 10 days.
Am I worrying too much about the scum, or does it indicate that the balance is wrong?
Many thanks for your advice!
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