I don't know what I am doing wrong - Red Macroalgae is not thriving

[iLikeAlgae]

Hi all,
I have a shallow bookshelf gallon tank where I keep Red Macroalgae, Codium and some easy corals.
I've had red macroalgaes for few months and they are not dying, and actuallve have grown quite a lot in size.
But they are are always in this ugly white, thin stretched state.

I use fluval reef 3.0 light, and the light setting is attached in the image. I tried both increasing and decreasing white and red light but did not help.

No3 is on the lower side(<2) but I try to feed every day. I have 2 small clown fish in the tank with some CUC; I tried feeding more often but I just ended up having more cyano.

Any advice is appreciated on how I can make my red macroalgae more lush and healthy.

 

[courtneykeeps]

Higher nitrates. <2 is way too low for a macroalgae tank.

Feeding is not really a great controlled way of increasing nitrates so I would try dosing nitrates specifically.

 

[EnterName]

Don't dose nitrate, dose ammonia.
Nitrate has to be converted back to ammonia before it can be taken up.

https://www.reef2reef.com/threads/diy-ammonia-dosing-for-low-nitrate-systems.987087/

That being said, 2ppm nitrate is still much higher than natural ocean levels. This means it's probably not the limiting factor here.

Trace elements might be. Iron for example needs to be added pretty much daily to be not a limiting factor as there are so many important biological processes that require iron. Other trace elements that might play a role for red algae to grow are manganese (used for photosynthesis), molybdenum (used for the previously mentioned nitrate reduction), cobalt (part of vitamin B12), and some others like zinc, boron, and iodine but I can't remember their exact use right now.

An ICP-MS test would show you what your tank is missing as you don't necessarily want to add something if you aren't sure it's actually missing.

However, I would expect other algae to have the same issue in that case.

I hope this still helps

 

[Mr. Mojo Rising]

IMO turn the lights up (that is not a strong light) and turn up the flow. Without enough flow, detritus builds up on the macro algae. The cyano growing on the side glass and flat water surface also shows there is not enough flow.

 

[Subsea]

At a minimum, I would dose iron. Also, consider dosing “chaeto grow”