blue-green algae (Causes and Cures)

>From: KB Koh <KB_Koh at ccm_ipn.intel.com>
>Date: Tue, 11 Jul 95 14:14:00 PDT
>Subject: blue-green algae
>Blue-green bacteria has started to appear in my tank a couple of weeks
>ago. It started below the gravel surface beside the glass and moving
>upward. They only appeared at certain spots in my tank. 
>Q:Should I be alarmed by this? 
>I've read the FAQ and articles in the Krib but there is no precise 
>rule mentioned to prevent them. There are hints here and there. 7
I wouldn't become overly alarmed and "freak," but then again, I would
take this seriously.  The appearance of Blue-Green Algae means
that something is wrong in your conditions in either the water quality
(conditions) or lighting.

>Q:I would like to know what level of measurable water quality to keep 
>them in check and prevent them from taking over my tanks. 
>My data:

>50gal with 80W lighting and Fluval 303 filter. Lighting 12 hours daily
>+ influx of daylight up to 10am.
>Water change 20% weekly, add Tetra FloraPride, Natrium Bicarbonate
>Tetra Crypto - 2 tablets forthnightly
>pH about 7.0
>Ammonia and Nitrite = 0
>Nitrate <12.5ppm (resolution for Tetra test kit)
>Major plants are hygrophilla difformis, various Echinodorus sp., 
>aglaonema, limnophilla sp., ludwigia repens etc.
>Fishes are 4 zebra danios, 2 black mollies, 2 corycat, 1 pleco,
>1 flying fox, 2 bumblebee gobies and just yesterday added 3 pencil
The two major causes of Blue-Green Algae is poor water quality 
(nutrient rich water), or dim (low)  lighting.  From your data it does not
appear that you have either, problem, however, you may still have one
of these 2 problems.  When did you change your bulbs last, and 
what kind of bulbs are they (spectrum, intensity, brand??).  If they are the 
wrong spectrum, and/or if they are old and therefore getting
dimmer (as florescent bulbs do when they get older), then you may 
have a lighting problem.  If the bulbs are more than 8-9 months old,
replace them.   If they are not a suitable spectrum, replace them (I would
be happy to try to help with determining this, if I can...).  

Even though you change 20% of your water weekly, you may still have a
water quality problem.  You may be overfeeding your fish.  There aren't
many fish in the tank and it would be easy to be putting to much food
in the tank, which would make the water to "nutrient rich" and degrade 
water quality.  Even experienced aquarium keepers can easily put
to much food in the tank.  Use the "only put in what they consume in 
5 minutes" rule.  If when you clean the gravel, and there is a LOT of 
"junk" in the substrate, this could be excess decomposed food.

Since you are using Plant Food, you may be using to much.  This can 
degrade the water as well.

>Q:I would like to add 8 cardinal tetras, 4 corycat and 3 glass
>cat in the next one month. Would this aggravate the situation?
>I would appreciate any response to this mail. Thank you in advance.

I do not think that adding these fish will aggravate the situation.
Since Blue-green Algae is really a bacteria, you can approach it as 
you would any other bacteria.  You can use Antibiotics on the tank to
kill it (for example).

"Heaven  = Fish + Magic (more than a card game) + Music + Shopping + Cars"
jayme_donnelly at percussion_com