Dr Mike Oxgreen
Member
I have been unimpressed with the plant growth in my 20 litre tank since it was planted about 4 or 5 weeks ago. Plants seem to be surviving, but not thriving. My light is generous, and I have no significant algae.
Even supposedly "easy" stem plants like Hottonia palustris are not romping away as I would expect. The tissue culture of Rotala walichii has grown a lot, but the growth lacks the lush feathery quality that I would expect. The tips have gone a slight coppery colour, but not a rich pinky-purple. There are two plants doing well: the Eliocharis acicularis "mini", and the Amazon Frogbit which I added 4 or 5 days ago (the latter is growing at a rate that might begin to scare me).
I’m pretty sure my CO₂ is okay, and I have repositioned my spray bar to give good distribution - the bubbles from the Twinstar M3 can now be seen sliding down the front glass. (Being able to visualise the water flow has been a major plus of having that device, and prompted me to improve my flow).
I’m beginning to point the finger at fertilisation. I’ve been dosing TNC Complete, using the 3x dosage which supposedly approximates EI. But I’ve just done some sums, and I’m not sure it does.
According to the analysis of TNC Complete, it contains the following:
N - 1.5%
P - 0.2%
K - 5%
So, taking an imaginary tank of 1,000 litres (i.e. 1,000,000 grammes), the 3x dosage of TNC complete would be 300ml weekly. Therefore our dosage contains the following:
N - 4.5g = 19.9g NO₃⁻
P - 0.6g = 1.8g PO₄³⁻
K - 15g
Now if I understand correctly EI calls for 20ppm NO₃⁻ so the above dosage is indeed correct.
But EI also calls for 3ppm PO₄³⁻ so the above dosage is significantly under.
Likewise, EI calls for 30ppm K so again the above is significantly light.
Is it possible that my plants are deficient in PO₄³⁻ or K? When I do water changes, I use about 10 litres of rainwater with 2 litres of tapwater to get the softness I want, so I’m not getting much contribution from the tap.
Should I increase my dosage of TNC Complete, or should I bite the bullet and start using DIY salts?
Even supposedly "easy" stem plants like Hottonia palustris are not romping away as I would expect. The tissue culture of Rotala walichii has grown a lot, but the growth lacks the lush feathery quality that I would expect. The tips have gone a slight coppery colour, but not a rich pinky-purple. There are two plants doing well: the Eliocharis acicularis "mini", and the Amazon Frogbit which I added 4 or 5 days ago (the latter is growing at a rate that might begin to scare me).
I’m pretty sure my CO₂ is okay, and I have repositioned my spray bar to give good distribution - the bubbles from the Twinstar M3 can now be seen sliding down the front glass. (Being able to visualise the water flow has been a major plus of having that device, and prompted me to improve my flow).
I’m beginning to point the finger at fertilisation. I’ve been dosing TNC Complete, using the 3x dosage which supposedly approximates EI. But I’ve just done some sums, and I’m not sure it does.
According to the analysis of TNC Complete, it contains the following:
N - 1.5%
P - 0.2%
K - 5%
So, taking an imaginary tank of 1,000 litres (i.e. 1,000,000 grammes), the 3x dosage of TNC complete would be 300ml weekly. Therefore our dosage contains the following:
N - 4.5g = 19.9g NO₃⁻
P - 0.6g = 1.8g PO₄³⁻
K - 15g
Now if I understand correctly EI calls for 20ppm NO₃⁻ so the above dosage is indeed correct.
But EI also calls for 3ppm PO₄³⁻ so the above dosage is significantly under.
Likewise, EI calls for 30ppm K so again the above is significantly light.
Is it possible that my plants are deficient in PO₄³⁻ or K? When I do water changes, I use about 10 litres of rainwater with 2 litres of tapwater to get the softness I want, so I’m not getting much contribution from the tap.
Should I increase my dosage of TNC Complete, or should I bite the bullet and start using DIY salts?
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