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Old 05/05/2014, 04:48 PM   #9
DiscusHeckel
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Join Date: Dec 2009
Location: Sheffield, UK
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My cyanobacteria diary (with a happy ending)

This post is a summary of events (extracted from my log book) related to cyanobacteria infestation in my tank and is essentially a note to self.

The problem began on 7th August 2013 when I came back from my summer vacation. All my corals were OK, but their polyp expansion was rather poor and their colour was rather pale. This was not surprising because I instructed my neighbour not to feed my fish heavily.

After a short period of cogitation and rumination, I decided that in order to improve my corals' vigour I needed to provide more food to them. Thus, heavy feeding of fish commenced on 10th August 2013 (up to four times a day using frozen food only). After only five days, I noticed significant increase in poly expansion. I was therefore on the right track. In addition to feeding fish heavily, I also fed my corals with Salifert's Amino acids once a week (using the suggested maximum dose).

First signs of cyanobacteria appeared on rocks on 27th August 2013. I did not do anything about it and continued to feed heavily while continuing to dose Amino acids, iodine, iron and potassium (as and when required). GAC and GFO were fluidised on and off until 23rd December 2013, which was the date when I stopped using them completely. The end result was that the corals looked really healthy, their colouration and growth improved significantly.

Looking back, my strategy, which was based on heavy nutrient input and export, had a major flaw in it. That was that I do not think I was able to export as much nutrients as I introduced to the tank. Because chaeto in my sump grew vigorously, nitrate and phosphate test results were really low (NO3 0-0.1 ppm; PO4 0-0.008 mg/l) and there were no green hair algae on rocks, I mistakenly thought that I was exporting enough nutrients to offset the heavy feeding. My mistake was to ignore one of the major signs of rapid organics build up, cyanobacteria [1].

For the sake of my corals and fish, I continued to feed my fish heavily, but the cyanobacteria problem lingered on. On 26th MArch 2014, I eventually decided to do something about it as it had started to annoy me. Rest of this post provides a summary of what I have done so far and the interim results:

STEP 1: Stop dosing amino acids, iron, iodine and potassium (REASON: Like all bacteria cyanobacteria need nitrogen, iron, iodine and potassium as food source)

STEP 2: Fluidise GAC (ROX 0.8) (REASON: Good quality GAC is a lot more efficient in reducing DOCs than a skimmer)

STEP 3: Fluidise GFO (Rowa Phos) (REASON: Even though cyanobacteria are capable of extracting PO[sub]4[/sub] extracellularly from organics, reducing it to a fairly low level will help)

One of my worst fears is to cause RTN/STN on my acroporids. My excessive use of GAC and GFO in the past sometimes resulted in RTN/STN. For this reason, I have been using fairly modest amounts of GFO and GAC. I try to replace GAC every 14 days and GFO every two/ three weeks.

STEP 4: Start to use Seachem purigen (REASON: This product is known to reduce organics)

STEP 5: Reduce feeding from up to 4 times a day to twice a day (REASON: To address nutrient input and export balance. I did not want to reduce feeding once a day or stop feeding altogether because this would have harmed established "good" bacteria)

STEP 6: Stop/significantly reduce the frequency of water changes (REASON: To deprive cyanobacteria of trace elements, which it may require to thrive)

INTERIM RESULT at 16/4/2014: Unsuccessful :annoyed:

I had the same cyanobacteria problem twice before (once in my nano tank and once in my second tank). The steps, which I outlined above, always worked for me. For this reason, this is what I always recommend people they do when they experience cyanobacteria. The only difference this time round must be to do with the fact that I never fed my fish as heavily as I did this time round and that I never allowed cyanobacteria to get a firm grip in my previous tanks and took measures before they got out of hand.

Inevitably, new measures were needed to address the shortcomings of the existing steps outlined above. I therefore introduced three further steps on 17th April 2014.

STEP 7: Install 100 micron filter sock under the main drain and clean it every day (REASON: Remove detritus to starve cyanobacteria and remove red slime to prevent cyanobacteria from restablishing themselves)
STEP 8: Clean my skimmer's collection cup and its neck every day (REASON: To improve the efficiency of the skimmer to remove more organics than before)
STEP 9: Remove detritus and cyanobacteria slime from rocks/glass floor by blowing them with a turkey baster [2] and brushing known trouble spots with a tooth brush every day (REASON: Remove detritus to starve cyanobacteria and remove red slime to prevent cyanobacteria from restablishing themselves)

INTERIM RESULT (21st April 2014): Positive but not conclusive

After the lights come on, cyanobacteria no longer show up immediately if at all. I have noticed that coralline algae have already started to grow on some brushed surfaces, which were previously occupied by cyanobacteria. On some surfaces, cyanobacteria no longer show up before brushing and blowing commences.

INTERIM RESULT (27th April 2014): Almost cleared

The new procedure (i.e. STEP 7 to STEP 9) is clearly working. I reduced the frequency of basting of rocks from every day to once every three days. The only place I can see signs of cyanobacteria is sand around the giant snail shell. The wrasse splashes sand from inside the shell while getting in and out.

I have also started to change water in regular intervals (~12% every 6 to 7 days).

FINAL RESULT (2nd May 2014): Cleared

The new procedure (i.e. STEP 7 to STEP 9) has worked. In order to find out if cyano woud reappear, I did not baste my rocks for six days. I did not use a filter sock either. Fortunately, cyanobacteria did not reappear. Interestingly, as the cyanobacteria subsided I started to get green algae growth on glass (not hair algae). I guess that eradication of cyanobacteria, which are great nutrient sink, increases the amount of nutrients in my tank, which then encourages other life forms to take cyanobacteria's place. There must be a shift of balance going on in my tank at present, which is a welcome development. It is such a relief that I have addressed the problem without resorting to chemicals or potions.


[1] I do not believe that Redfield ratio can be one of the main causes of cyanobacteria because cyanobacteria can fix nitrogen and phosphorus even when nitrates and phosphates are very low in surrounding waters. They fix these life building elements extracellularly from organics. Hence, the reduction of DOCs is of paramount importance if battle against cyanobacteria is to succeed.

[2] Big E (Ed) suggested this method to me.


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