HC dying after growing really well (Cyanobacteria growing)

Hello,

I am having a problem with my HC dying. I started using the dry start method (mainly to get it rooted). After I flooded the tank everything was going great for about 1.5 months. The HC and DHG grew to carpet the entire area with lush growth. There was a problem with brown slime algae (diatoms I believe) but nothing major.

However after that the growth just seemed to stop on the HC. I also started getting green water and cyanobacteria. The DHG is still growing and looks great. The HC is slowly melting away.

I don't have any fish in the tank. I started the filter on my established 30gal for one month. I tested for ammonia but didn't find any. I tried a black out but it didn't help with the cyanobacteria (maybe it was not a complete enough blackout). I reduced my light intensity to combat the GW and cyanobacteria. I also tried upping the EI dosing. The HC is still dying.

My tank parameters/set up are as follows:

- Standard 10gal
- Two 20W GE 6500k spiral CF mounted vertically ~6" from the top of the water in desk lamps (I started with two 26W GE 6500k spiral CF before reducing to 20Weach to help with algae)
- 8hour photoperiod
- Eheim 2211 filter
- Iwaki pump running Cerges style CO2 reactor (~250gph)
- ~25C temp
- EI dosing (10.9ppm NO3 + 4.25ppm PO4 + 12.6ppm K + 0.16 Fe (through Plantex CSM+B) 3x per week with 50% water change at the end of the week) Using this calculator: http://calc.petalphile.com/
- Dosing was less before I increased it (doubled)
- Tahitian moon sand substrate with osmocote plus at the bottom

I would like to try and save it before it all dies out. It had formed a really nice carpet. Any help to get that back would be appreciated.

Thanks,

Daniel

 

I trimmed the HC once when it was growing well. It bounced back just fine.

I don't know what the CO2 level is. I just turned it up high in the start (as I have no fish in the tank). I assumed since the HC grew really well for the first ~1.5 months that it was high enough. When it stopped growing, I increased the CO2 but it appears to have done nothing.

Daniel

 

I clean the filter twice a month. I also clean inside the tank every time I do a water change. Perhaps the filter needs to be cleaned more?

To my knowledge I never intentionally changed anything as both plants were doing really well.

The only thing I can think of is that when I first flooded the tank, I used the water from my 30gal EI dosed tank when it was due for a water change. It might have meant I started with high ferts and as I did water changes they slowly dropped off to insufficient levels.

I assume it is best to increase one at a time (CO2 or Ferts) to see which is the cause, or should I increase both at the same time?

Thanks,

Daniel

 

I did trim it when it was growing well. It bounced back just fine. I don't think that was the problem.

Daniel