DPH Tank Cyano Bacteria or Not and What to Do About It
written by: Rob Charite
date: 31 August 2000

After a good and detailed investigation I came up with the following, (although I could be wrong) :) cyano bacteria mostly occurs in badly maintained tanks. You can recognize the first signs by the smell of rotten eggs due to poor bottom substrate conditions. When you poke the bottom area with a stick or what ever you see bubbles rising to the surface. Mostly in places where the water's flow rate is very low. In bad situations it could cover all the plants, wood and other possible ornaments. Since the tank doesn't show any signs of the cyano bacteria it must be something else. So I roamed the net a bit, asked here, read there and came up with the following.

Cyano bacteria species are free floating and the colonies that do not attach to surfaces can "fix" nitrogen gas. They take Nitrogen gas (from the air) and transform it into nitrates or ammonia and release those into the water!!! :( This is why Blue Green algae is so hard to get rid of, it can feed itself. Cyanobacteria also needs Phosphorus, nitrates and trace minerals to grow. That, and light!!!

The problem now isn't cyano bacteria, but "good" green hair algae, the "dreaded" algae mostly common in healthy tanks. So the first thing I did was decrease the light 4 hours a day maximum. I can tell you that helps, but only for a short while 'cause algae don't need much light and reappear within one week. So back to nothing, I decided to increase illumination to it's full potentional, yes, the full 12 hours with a total of 150 watts !!

Why? you may ask :)
Well, let me tell you this: plants suffer from the lack of light and algae loves suffering plants as a home. So instead of attacking the algae I decided to give them what they want :) nurture them that is. Mean while I bought a new filter, nice one, with a bigger flow rate and bio surface.

What happened is the following :)
I increased the CO2 injection to its limit (almost) that is 23 mg/l with a KH of 5. The result was a pH of 6.8 that was the max. And added 8ml iron fertilization every other day and I was really amazed; the plants love this !!! Why 23 mg/l ? Fish can't cope with levels above 30 mg/l and will suffer from CO2 poisoning and since I adore the safe side I kept the amount at 23 mg/l. Using the CO2 and iron as fuel along with the nitrates and phosphorus they grow like hell.

I can tell ya algae don't like that !!!!
So the only algae that is left is some "dreaded" algae, (nice beautiful green when kept short by an ancistrus) and some free floating tiny hair algae (aprox 2 - 3 mm in size) which I am not sure what it is (update later) but it can't be bad 'cause it isn't blurring my water or affecting the fish.

Meanwhile, the tank is crystal clear again and back to his original state, although I changed some things. So the moral of this story is: :) when keeping a planted discus tank it is very, very, important to take proper care of your plants 'cause they are the key to failure or success and they do have a lot of influence on the water parameters and therefore the fish !! Needless to say the maintenance regimen is important too, for both fish and plants.

Rob Charite & Walter Soestbergen