Cyanobacteria In Flooded Dsm Aquarium

Hi guys,

A few months ago I planted a tank and covered it using the dry start method. Then abandoned it for like 6 months. After weeding out some emersed weeds, I flooded the tank.

The plants are hairgrass, covering about 40% of the substrate currently and several stems of what I think is some type of rotala.

The hairgrass is very dense in some areas and very scarce in others.


I’m on week 2 and I have patches of Cyanobacteria growing in the substrate, this Cyanobacteria was introduced when I used tap water (my tap water has it apparently). I have since switched to filtered drinking water that I buy in 5 gallon returnable bottles, and the algae was receding but now it’s staying. There’s some diatoms as well but I find they always disappear on their own.

I’ve heard I should either reduce phosphates or increase nitrates... problem is my ferts are combined NPK, I can’t choose how much of each one I dose. Should I just dose more NPK and hope for the best?

Here are some measurements and specs of the tank:

Substrate: fluval plant and shrimp stratum
Aquarium: Mr. Aqua 12 gallon long (36”x9”x8”) it’s not the real deal, I had one made to the same measurements cause I can’t import the real deal
Filter: Aquaclear 20 on the right corner and Hagen Elite Mini filter on the left corner, acting as a nano powerhead. I have active carbon on the aquaclear because it was a new tank. I don’t know how much it affects the chelated minerals in the micros.
Fish: 6 newly introduced cardinal tetras (2 days in tank)
Light: Finnex 24/7 Planded Plus SE
CO2: pressurized tank, with diffuser


Nutrients:
Light: hard to define the photoperiod because the light fades in and out, but I will say 7-8 hours of effective photoperiod, and 3 hours of ambient light (the lights are at minimum brightness during these 3 hours)
CO2: 30ppm.
Other carbon: 1ml to 1.5ml of flourish excel daily. Helped eradicate some string algae.
Macros: a friend gave me a mix of what I think is GLA macros for EI method. It’s NPK mixed together. I dissolved this into a bottle with drinking water.
Micros: GLA CSM+. I dissolved these into a bottle with drinking water.
Dosing regime: EI method. Monday macros, Tuesday micros, Wednesday macros and so on. 50% change on Sunday.


Water parameters:
Before introducing the fish last Monday, I measured my water parameters. It was 24hrs after a water change and I dosed macros that day. This is measured with API liquid test kits.

pH: 6.0
Ammonia: <0.25ppm
Nitrites: 0ppm
Nitrates: <5ppm, I estimate 2.5ppm
KH: 2dKH
GH: 1dKH

As you can see, it’s very soft water, but it’s not RO/DI. I am a bit worried about the fact the ammonia was not 0ppm and that the nitrates were so low for a planted tank. Any comments?

Let me know what improvements I could make to try to get rid of this nasty bacteria. Hopefully it won’t come back.

 

Okay, first thing I'm gonna do is remove the last 3 hours of ambient light.
I have a window nearby with a shade and a curtain. I have noticed that from 8AM to 11AM some sunlight gets through. I used to keep the shade down but now I'm using the curtain (so 0 light from that window) and it has made a difference as well.

I'll try to find KNO3 on a gardening store. Any recommendations on how to calculate the dosing of it? I saw on the internet that is often sold as a pure salt.

 

It was receding but it's back again. I must continue to remove it by hand

I did remove the last 3 hours of light at night, I don't know if it had to do with this.


Edit:

Thinking about the changes I have done since last week, I found the following things:
* I have started to feed the fish more since they have acclimated and are feeding more aggressively. I'll reduce the feeding once again, as long as they don't lose weight.
* I have stopped using the air conditioner at night so the temperature is a bit warmer (the aquarium is unheated because I'm in the tropics anyway). The lack of AC might have accelerated the cyanobacteria reproduction.
* I have noticed a find of foam or scum on the surface of the water, which might be affecting the oxygen levels. I have tried to remove this but it's not easy to get rid off without a skimmer. I'll try to remove it more aggressively.

I also increased the flow on the powerhead.


Edit 2:

Just found out that my sister fed the fish quite a lot earlier in the day, that must have been the problem that triggered the algae. I did a 15% water change siphoning out all the excess food and some algae. I wanted to change more water but that's all the water I have prepared and ready to go.

Hopefully I'll get back on track by next week.

 

Thanks HHLaursen! I shall try it as my last resort, because the plants are doing so well I don’t want to hurt them. However, I think I could cut back on food for a few days, given that my sister naively added lots of food today. It’s okay though.

I also like the idea of hydrogen peroxide, more than the blackout to be honest.