Oily surface scum on new tank - reducing light

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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!
 
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hogan53

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Hi
I wouldn't bother with adding ammonium chloride!
Just purchase very fast growing stem plants like
https://www.ukaps.org/forum/plantbase/hygrophila-difformis.93/
https://www.ukaps.org/forum/plantbase/hygrophila-polysperma.95/
https://www.ukaps.org/forum/plantbase/limnophila-sessiliflora.106/
You will source these usually at the local aquarium shop.
Plant some, leave some floating on the surface....this will be far more beneficial for maturing the aquarium, also probably quicker!
Scum is down to the balance not being quite correct!
You can purchase a small skimmer to remove the scum!
https://www.amazon.co.uk/All-Pond-S...quarium&qid=1582884154&sprefix=skimmer,aps,15
41ZM0zg9f4L._SY355_.jpg

hoggie
 
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Hi
Quote.....Fert: TNC complete.
The above should be a weekly dose!
Or 3 times per week, not daily dosing.
hoggie
Instead of dosing every other day, I am dosing half every day.

So the standard weekly dose is 1ml per 10 litres, i.e. 2ml for my tank.

To approximate EI, you can dose that 3 times a week. For my tank, this would be 6ml spread through the week.

But instead of dosing 2ml three times a week, I choose to dose 1ml every day, which is 7ml spread very evenly through the week. Since the whole point of EI is to ensure plentiful nutrients, I’m pretty sure an extra 1ml per week isn’t going to do any harm.

More importantly, dosing every day also means I’m much less likely to forget!

If you feel the extra 1ml is a problem, I could always miss out the dose on water change day.
 
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dw1305

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Hi all,
I’m dosing Dr Tim’s ammonium chloride and waiting for the cycle.
I wouldn't bother with adding ammonium chloride!
Please stop, it is going to cause all sorts of problems. You plants will take up some of the ammonia, but you aren't short of nutrients and they definitely need any more nitrogen.

Planted tanks never need cycling with ammonium and once you've planted them it is definitely going to do more harm than good. In fact the entire cycling premise is based upon research that has been superseded by more recent scientific research. You don't have to take my word for this, you can read Tim Hovanec's comments in <"Bacteria revealed">. I've got a lot of time for Dr. Hovanec, he has revised his views in light of scientific advances.

Have a look at page 4. of <"Bedside Aquarium">, it links into plenty of the recent research on nitrification.

cheers Darrel
 
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So is Dr Tim Hovenac the same person who is still using his name to make money from a product founded on science that he himself has renounced?

If so, isn’t that a teeny bit unethical?

A quick Google suggests that it is indeed the same person. I actually feel rather cheated!

I’m perfectly willing to accept that the science has changed, although I was unaware of it. Although I don’t have time to read all the papers, the very existence of peer-reviewed papers that render my previous understanding incorrect is good enough for me.

Perhaps my next steps should be large scale water changes over the next few days to rid the ammonium, but, er... then what?
 
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hogan53

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Hi
Purchase some fast-growing stem plants which will help cycle and build up beneficial bacteria, then test for ammonia every week before and after water changes!
Meant to say you may have to pack the skimmer with filter wool, as the flow may be a tad high for a 20 litre aquarium!
Cheers
hoggie
 
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Okay, and in a couple of weeks’ time when my plants are reasonably grown-in and I haven’t seen any ammonia (or nitrite), then I’m ready for the first inhabitants?

I’m guessing perhaps 2 or 3 Amanos might be a suitable start, being very low bio-load?

Ultimately I’m planning on half a dozen ember tetras, and a colony of cherry shrimp. I’d probably leave the cherry shrimp until the tank is a bit more mature.
 

dw1305

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Hi all,
So how do I know for sure when my tank is ready for fish?
That is actually the easy bit, once the plant mass is in active growth and reasonably established you can add the livestock. I like six weeks growing in, and to add the fish fairly slowly, but that is probably a <"fairly cautious approach">.
I’m not sure what harm it’s going to do?
Purely in terms of nitrification, the more recent research has shown that the nature of the microbial assemblage is very sensitive to changes in ammonia level, and that the micro-organism assemblage found in aquarium filters doesn't include the canonical ammonia oxidising bacteria that were isolated from sewage. There is a fuller description, and some links to papers in <"Tanks without fish">. Since people have been able to look for the specific ammonia and nitrite oxidising genes the range of organisms involved in nitrification, and the metabolic pathways utilised, have increased exponentially.

The other issue with ammonia and light is that you are likely to trigger algae "outbreaks". Have a look at @Cor's <"Cycling without plants thread">
So is Dr Tim Hovanec the same person who is still using his name to make money from a product founded on science that he himself has renounced? If so, isn’t that a teeny bit unethical?
You would still need to use ammonia based cycling if you intended to keep a tank with a high fish load and no plants, and so were reliant on microbial nitrification. Personally I'm never going down that route. It maybe that the production methods for his <"microbial supplement"> has changed and it does include the relevant Archaea and Nitrospira spp?
Perhaps my next steps should be large scale water changes over the next few days to rid the ammonium, but, er... then what?
Nothing really, just keep on going as you are, I'd add some stems as per @hogan53's suggestion.

Do you still have the Hornwort (Ceratophyllum demersum) from your other tank? It is a great fast growing stem.

cheers Darrel
 
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Thanks Darrel, I will follow up your links!

I took your advice and have ceased ammonium dosing, and did a major water change today. I don’t know if it’s coincidence, but the water surface is like glass at the moment.

I did actually have a few sprigs of hornwort in there. I removed it because the scum appeared very shortly after I added it, but that was probably coincidence. I still have those sprigs so they can go back in, and I can fish some more out of the pond (and carefully pick off every tiny trace of duckweed, which will totally infest my tank - I hate that stuff with a passion!)

Fair enough that ammonia dosing would be the only humane option for cycling a fish-only tank, I hadn’t thought of that!

Many thanks!
 
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I’ve just picked out a massive load of hornwort from the pond. While I was there, it was pleasing to note some serious newt activity - spring is on the way!

So the hornwort is now in the tank, and I think I’ve also introduced the first critters - some kind of thing that looks like a flattened woodlouse. I’m not too worried about them, but will be keeping a sharp lookout for any bits of duckweed.

Presumably, bringing hornwort from the pond will enhance the microbial diversity in the tank, which I would hope is a good thing.
 
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I run a airstone at night, breaks up the water surface and gets rid of any scum problem. I also had some unhappy fish that use to gasping at the surface. If you have a ehiem airpump inside your cabinet there almost silent.
 

dw1305

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Yep, Asellus aquaticus is the little fella!

Ah, now, I did also see a sort of worm-like thing kinda worming its way across the glass yesterday. The Google search for Planaria might be a hit. Should I squish it if I see it again?

In the past I have seen Hydra too. Amazing things, and probably only a threat to fry and baby shrimp. I think...

Oh, and naturally I’m pretty sure I’ve seen at least one seed shrimp. I think that’s par for the course.
 

sparkyweasel

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Should I squish it if I see it again?
Planaria have a fantastic ability to regenerate, tiny pieces can each grow back into a complete animal.

They mostly eat snails, so you might want to remove them if you want to keep fancy snails. A small piece of meat will attract them, leave it overnight and you can pull it out with the planaria still attached.
 
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So, returning to the question of my surface scum... it’s still an issue.

I’m interested in understanding and removing the cause, rather than removing the scum with a skimmer or air pump. If the scum is being generated by stressed plants, then it’s trying to tell me something!

In response to the comments on this thread so far, I did a 50% water change on Friday and a 75% change on Saturday. I now have 0 ammonia, 0 nitrite, and less than 20 nitrate. TDS is now about 140.

But this morning (Sunday), the scum is back.

Should I continue with the lower light level, or should I lower it further? If the scum is being generated by stressed plants, can I expect an immediate improvement if I lower the lights, or is this something that will continue for a while even after I’ve found the right lighting level? So far I haven’t seen much improvement.

Should I even try a blackout to see if the scum is still generated?
 
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Okay, I’ll reduce the intensity. Do you know if the secretion of oils will reduce/stop immediately, or is it a slow process? Just so I know when I can judge success of the strategy!
 
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