Help turning my Rotala 'Vietnam H'ra' red?

nuture92

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28 Jun 2020
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Location
London
Hello! I'm having difficulty turning my Rotala 'Vietnam H'ra' red in my nano tank. At the moment, only the underside of my leaves are a lovely light pink colour, and the tops are almost entirely green. The plant has never been red, and I've been growing it for around 6 months.

From my initial research, it seems like switching my fertilisation from TNC Complete to a bespoke mix with reduced N and increased Fe might worth a shot? However, I could easily be missing something obvious, so please let me know.

Tank specs:
  • Size - 20L Dennerle Nano Cube
  • Filter - Oase FiltoSmart 100 External Filter
  • Lighting and duration - ONF Flat Nano +, 8hrs 100% (previously 80%)
  • Substrate - Dennerle - Scaper's Soil
  • Co2 dosing - 1 bubble/second
  • Fertilisers - TNC Complete, 2ml, 3x per week
  • Water change regime - 2x 80% water change per week
  • Plant list - Rotala 'Vietnam H'ra'
  • Inhabitants - None
I have been dosing TNC Complete, 2ml, 3x per week for about a month. Previously, I was dosing around 2ml, 1x per week. The most obvious change I can see is more rapid growth - stems grow at around 6-7cm per week.

Many thanks for any advice.

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Witcher

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15 Jan 2020
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London
However, I could easily be missing something obvious, so please let me know.
Hey @nuture92 I think you're introducing too much Nitrates with your water changes. London tap has typically between 25-35ppm nitrates, with every 80% water change you're constantly adding approx. 30ppm of NO3 and your rotala (and vast majority of red plants) need approx 5ppm or below to start turning to shades of red/burgundy etc. (plus it needs strong light). I'd personally reduce W/C to approx 10-15% weekly, wait few weeks till all built up nitrates will be depleted and then you should start to see some effects. Bear in mind that with your TNC you add even more NO3 so probably your dosing regime needs to be looked at as well.

Other option could be investing in RO or collecting rain water and reminalising it from scratch to the desired levels of hardness and nutrients.
 

nuture92

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Joined
28 Jun 2020
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Location
London
Cheers both, really helpful.

Hey @nuture92 I think you're introducing too much Nitrates with your water changes. London tap has typically between 25-35ppm nitrates...
You're absolutely right; I found the Water Quality Report for my postcode, and the mean mg/l of nitrate is recorded as NO3 is 30.9.

In a stroke of luck I happen to be moving up to Edinburgh shortly, and the Water Quality Report for my new postcode records the mean mg/l of nitrate as NO3 as 1.58!

According to the barr report's calculator, TNC Complete is 3.75ppm/degree at recommended EI dosing, so it seems like it still could be useful for me to switch dosing regime.

I will update this thread with pics :snaphappy:.
 

nuture92

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Joined
28 Jun 2020
Messages
6
Location
London
so with my tap water at 20 no3 would red plants be a non starter or would it be a case of less frequent water changes in the hope the no3 is used up
I'm also interested in how long it would take a heavily planted tank to reduce nitrate levels from WCs. I found this on Aquasabi:

...In densely planted aquariums or aquascapes, the nitrate consumption can get so high, that a dedicated nitrate fertilizer has to be added, to prevent deficiency symptoms and growth defects. In some cases, an aquarium with many fast-growing plants can have a daily consumption of up to 5 mg/l NO3, meaning that a plant aquarium should have a nitrate concentration of 10 to 25 mg/l NO3. Significantly higher levels are not detrimental to aquatic plants, but there may be a change in colour, e.g. some reddish plant species tend to turn a greener hue.
Which suggests it would be possible to reduce your nitrates to hit that 5-10mg/l NO3 target - depending on how much you're willing to skimp on water changes and the volume of your tank.

Another thing you might want to consider is finding red plants that remain red in almost all conditions e.g. Alternanthera
 

nurture92

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4 Aug 2020
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Edinburgh
Warning: probably not interesting to anyone apart from me :cool:

This tank's been running in Edinburgh for 2 weeks now.
  • Fertilisers - EI dosing KH2PO4, CSM+B, K2SO4
  • Nitrates tank water test kit result: 0-5ppm
  • Nitrates tap water test kit result: 0-1 ppm
Through my likely-optimistic eyes, I feel like the the rotala is definitely taking on an orange-y tinge on the tops of leaves on the upper 50% of stems which is exciting!

However I've also just added some HC cuba, rotala macrandra and alternanthera rosaefolia so I hope the nitrate limitation doesn't stunt their growth too much. Will probs let this run for a couple more weeks and see what happens. Bad idea?

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