Above: Rotala 'Singapore' or Rotala 'SG' under different conditions.
A: Rising nitrate levels turn the newest shoots green/ yellow.
B: Medium nitrate levels- slight orange/ green new shoots.
C: Steep sustained nitrate limitation turn leaves dark red.
Similar to other members of the Rotala family ('colorata', H'ra', 'Ceylon' etc.), follow these steps for richer reds:
Use APT1 if you keep more fish, or APT 3 at half or one-third dosage if plant mass is low. Dosing calculator here.
Stronger light (>150PAR) for 7 hours.
Trim and replant the healthy tops the 2Hr Way.
Above: side view of Rotala SG (left-most bush). The same plant in the same tank exhibits different coloration as the tank matures (even when fertilisation- APT3 in this case-is kept constant).
In a newly planted tank, new tips are often orange/green as the plant is shorter (it receives less light) and nitrates are higher (lower overall plant mass).
As the tank matures and plant mass increases, nitrate levels drop naturally (from increased plant absorption) and in 'Summer' the plant is often deep red.
What NO3 measurement should I aim for?
<5ppm: With regular water change, keeping nitrate levels below 5ppm helps to keep algae at bay and generally signals a healthy tank.
0 ppm: In most 2Hr Tanks, nitrate levels generally measure zero. Not because we do not dose nitrates, but because the effect of nitrate limitation start to kick in at that zone (in taking water readings, we are always measuring only the residual level, after absorption).
So low nitrates is always good?
Nitrogen is actually a key growth factor for plants, in the same way that we need, say, proteins or carbohydrates. So less is not always beneficial, and the form it takes its important. For species that show better coloration with nitrate limitation, an easy path to success is APT 1 + APT Jazz.
Above: A lovely aquascape courtesy of a user. Rotala H'ra shows green tips when transiting to APT3 from a leaner fertilisation regime. This means nitrate levels are rising.
While this is temporary (plants will adapt to improved nutrition and residual nitrate levels will drop naturally as plant mass increases), we can also do the following:
Reduce APT3 dosage to half (or one-third).
Consider switching to APT1 (recommended if fishload is high).
How to transit to APT?
For tanks that have been grown very lean (most conventional fertilisers), follow these steps:
Consider APT1 + Jazz(the best time to add is when you replant the tops)
Start with APT3 at half-dose for the first 2 weeks and gradually increase.
Remember that nitrate levels are hugely impacted by fish feeding / fish waste. If nitrate levels are high, more moderate feeding often helps- alot.