Alternathera cardinalis flagging

[Brand]

I have a 300L aquarium, stocked with a variety of fish and several different species of plant, but I'm having trouble with alternathera. It is losing colour steadily, from the lower leaves up.

I run my tank on a full nitrogen cycle; I have an external filtration system which incorporates anaerobic, nitrate-processing bacteria. The nitrate level sits at around 20 - 30 ppm with no intervention on my part. I maintain CO2 levels using Easycarbo, and supplement regularly with other trace elements. I have several types of anubias, rotala wallichii, echinodorus ozelot, and eleocharis acicularis—all thriving, but I was advised that alternathera required nourishment via the roots, and have planted root tabs (two types) at their base, but they are slowly fading.

Does anyone have any advice?

 

[Gorillastomp]

It depends on what you mean by fading. Does the red goes to green or is it like losing its leaves ?

First, alternanthera seems to do better once its root system is developped, it takes a vit to do so. Around 2-3 weeks. Its a plant you don't want to cut the top and replant but cut atthe base abd let it regrow.

Second, if its losing its color (from red to green) it means either the light is too low or co2 is low aswell. Since you are using liquid co2, i assume you are around the low spectrum of the light. So it could be both. I do not advice to increase your light so you may end up with an algae bloom without co2 injection. It should go toward the red again near the top where it reach enough light while growing.

 

[Brand]

Sorry; when I say 'fading', I mean it looks as though it's dying. It's been in the tank for over a month, it hasn't grown at all, and its leaves are losing colour, some of them going brown in places. Some of the top leaves are affected, too. (I would post a picture, but I'll have to wait till it gets dark.)