Bga (cyanobacteria) And Lighting

[rikgarner]

(Also posted this at UKAPS.org, so apologies if you have already seen it!)

Hi All,
I have been fighting with BGA on my relatively new (three month old) high tech planted tank, and I was starting to run out of ideas until I read:

http/www.netpets.org/fish/reference/reef...obacteria3.html

Which suggests that lighting can be an issue. Although I have tweaked the photoperiod and the combination of lights on at the same time, I haven't examined the lighting as a whole.

My tank is 48"x12"x12" 120L-ish, and is currently lit with 3x30W tubes:

2x AquaGLO (http/www.hagen.com/uk/aquatic/product.cfm?CAT=1&SUBCAT=112&PROD_ID=01015850030101)
1x SunGLO (http/www.hagen.com/uk/aquatic/product.cfm?CAT=1&SUBCAT=112&PROD_ID=01015930030101)

Photoperiod is currently 1200-1600, siesta 1600-1800, then on again 1800-2200.

I am injecting CO2 with a D&D kit with the powerhead swapped out for a Rhinox 5000 at about 1 bubble per second, and my JBL drop-checker never shifts from dark blue.

7.0 pH
0 Ammonia
0 Nitrite
20ppm Nitrate (Higher than I would like but tap water is 20ppm too!)
13 GH
14 KH

Tank is dual-filtered, a Fluval 205 with bio media and sponges, and an eheim 2232 with purely mechanical media. Minimal surface agitation from water return.

20% changes weekly. I was dosing Seachem ferts until 4 weeks ago, after which I haven't dosed any to try and bring the nutrient quantities down.

Stocking is:
2 adult Gold Barbs
23 Cardinal Tetra (LFS couldn't count 20 )
5 Cardinia Japonica (Algae Eating Shrimp)

Is my lighting the problem? Are the two 14k tubes too much? Have I missed anything obvious? Would a UV unit help? This project has cost me hundreds already so a couple of hundred more would an annoyance but if that's what it takes...

Any advice would be greatly appreciated. If its not the tubes I don't know what else to do other than re-home the fish and scrap the tank as I'm completely disheartened.

TIA,
Rich

 

[Waterloo Kid]

I had this problem for a few years, to the point where it made the whole room smell.
I finally beat it by altering my lighting period. I have two sets of lights on the tank, 2x 40W T8s and 2x 54W T5s. Monday to Friday I have the T8s on for 8 hours a day with the T5s on for about 5 hours every other day. I also inject CO2 with the T5s at approx 2 bubbles per second. On the weekend both sets are on for 9 hours to boost the plants energy levels and to show off the tank better when I'm around. I dose a liquid fert once a week. Please bear in mind that most of the plants in my tank are slow growers apart from a stand of H. Polysperma and a HUGE Amazon Sword which is currently 60cm tall and about 70-80cm wide. I currently have no algae issues at all. My NO3 readings are always zero.

This is probably not the way it should be done, but I get persistant slow growth that's easily controlled, and happy fish!

WK