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nitrates, phosphates, algae and CO2 - Daphne - APD V4#1267


You are going in the right direction. Pearling is oxygen. The plants 
are photosynthesizing well. In all probability, the water column is 
oxygen saturated and is somewhere above 8 mg/L. This is happening 
because of the added nutrients, especially the nitrogen, in the 
presence of good light.

You might question the value of the UV sterilizer. It kills the 
nitrogen cycle bacteria. Every healthy aquarium I've seen has some 
valuable bacteria cultures. Although you have a low reading of 
Nitrite, this is an indication that there isn't nitrifying bacteria 
that will transform Nitrite to Nitrate.

Blaming Phosphate for algae proliferation is largely a mistaken 
notion. You have PO4 of .07. I have had a tank with 3 mg/L Phosphate, 
and had no algae. But, this tank had a full house of other nutrients: 
20 mg/L of Nitrate and 0.25 mg/L of iron complex with Potassium 
(somewhat equivalent to TMG). Having a good iron test kit is 
important. The only one I use is made by HACH. Costs a bit more. 
Haven't been comfortable with many of hobby level kits.

Algae thrive in poorer nutrient environments and higher plants don't 
do well when there are limiting factors with the nutrients. This is 
generally true. However, it is possible that algae can expand when 
more nutrients are added. The addition of nutrients perk up the 
higher plants, as seen with plants pearling (they are working 100%). 
But, during this transitional phase, the algae can also get a boost, 
and threaten to be the dominant species. To shift the emphasis away 
from algae to higher plant dominance, one needs to physically remove 
as much algae as possible. Take the driftwood out and scrape off the 
algae and rinse well. With a single edged razer blade, remove algae 
from the glass. As a transitional action, add a lot of fast growing 
plants like Rotala and Hygrophila difformis or Wisteria. The shear 
increase mass of higher plants, replacing the algae plants, may well 
shift the balance, and eliminate the algae.  I have used the 
technique many times, with success. Works every time.

You said: On a related note, my CO2 is still dropping to 6.4 at night 
yet it is set at
6.9 on controller.

I think you mean : the pH 6.4 / pH 6.9.  Controllers are set to turn 
on and off within a bracket. For instance: off at 6.8 and on at 6.9. 
At night the pH in the water can go below the setting of 6.8 because 
plants and algae respire and give off CO2 (lowering the pH) in dark 
periods and use up Oxygen then. This night time CO2 from the plants, 
could drop the pH below reach the controller. If this makes sense.