When Less is More

Above we have taken a section of Rotala rotundifolia originally grown on APT Complete (right) and grown it on APT Zero (left), which contains no nitrates. While both are 'red', the plant on the left is clearly 'pink', while the one on the right is more 'orange'.

Since less is more, can I simply do without ferts?

No. Rotala rotundifolia needs a complete, nutritious diet to be healthy.

So, just remove all nitrates?

No. The total absence of nitrates would result in stunting and poor health (which makes it vulnerable to algae)

So how?

The technique is to use fresh Aquasoil (as opposed to inert and synthetically enriched inert substrates), while adding a fertiliser that contains some nitrates, but only enough to bring out the colour. Aquasoil acts as a nutrient store, so some nitrogen is always available through the roots. Combine this with a leaner fertiliser and you have the sweet spot.

The stored nitrates in fresh aquasoil become depleted after around 3 months. At that point, you can either add fresh aquasoil, or enrich the substrate with a root fertiliser such as APT Jazz. 

So I should NOT use APT Estimative Index?

Exactly. The Estimative Index approach works for plants that thrive in nitrate-rich waters. With APT EI, your red Rotala will most likely be healthy, but not red.

So I should use APT Complete?

Probably. If you have a heavily planted tank, the resultant level of nitrates using APT Complete is generally low enough to induce 'nitrate limitation' (think of it as a Ketogenic Diet of sorts) to bring out orange-red tones you see above. However, if you have a small or less heavily planted tank, the nitrate level may still be a little too high. Try lowering the dosage or using APT Zero.

So I should use APT Zero?

Very likely. When paired with fresh aquasoil, or old aquasoil (> 3 months) that has been enriched using APT Jazz,  APT Zero delivers the 'sweet spot' combination of complete nutrition except nitrates and phosphates (available in aquasoil, and in fish waste). At these levels, you get the reddest possible outcome.

Is there a catch?

The nutrients in new aquasoil get depleted over 3- 6 months. It is best to use APT Zero combined with APT Jazz. 

Another fine point is that light strength matters, but so does spectrum. To bring out the tones you see below, you need either a T5 array with stronger Red and Blue tubes, or LEDs that have have sufficient red/ blue diodes to bring out the red tones.

Above: A tank with a variety of red plants using APT Zero in the water and APT Jazz in the substrate.