"Selective" algae growth

In my 90 gal. tank I'm seeing selective BBA growth. Some stem plants are looking terrific and algae-free, while other plants (jungle val., SOME crypt leaves, tank hardware) are heavily covered. Yes, I can and will trim off the growth, but my question is why? Why would some leaves (usually the older ones) accumulate algae growth but not others, and why some plants but not others?

Thanks

Tanksalot

 

Tom:

Thanks! That makes sense, especially since I've had quite a bit of growth in the last few weeks, as well as adding new plants.

I have a 90 gal. tank; 4 T-5's (right on top) and pH-controlled CO2 supplementation, using a Cerges reactor downstream of the return pump from a covered wet-dry. KH is about 3 -4. Prior to adjusting anything, I checked the pH meter calibration, and it was off by 0.3 - 0.4 (it was reading artificially low). Setpoint is/was 6.2. The drop checker (two bulb with a 4 KH standard) read a tad yellowish. Right now for the short term I'm going to let things go with a re-calibrated pH controller and see if the BBA growth stops, or do you feel otherwis

From what I've read on your site, I realize you're not a big fan of either drop checkers or pH-controllers, but there are many of us who don't have the keen eye for plant conditions that someone with your experience and knowledge has. Now I know to check CO2 if I see a wisp of BBA appearing.

But if you didn't have the experience you have, how would you proceed in adding a bit more CO2 to the tank?

Thanks for the help!
Tanksalot

 

Well, I've learned quite a bit. I cleaned out a lot of the BBA and overgrown stem plants. Reset the pH controller and waited until this A.M. to see how things go before I plugged in the controller.

Someplace I had read on a forum a response to the question "At what level do you set your CO2?" and one of the responses was "until the shrimp start jumping out". I thought he was kidding......he wasn't. I couldn't figure out why the shrimp seemed so determined to crawl into the overflow, then I saw a cardinal in there and the light went on (in my head). Fortunately I didn't lose anything, and things are now stable. Other than re-calibrating the pH controller the only other change was a 40% or so water change.
It doesn't seem reasonable that I should have to run "so close to the edge" with CO2. Do you see it differently?

Now as far as I see my other options are Excel dosing and shorter photoperiod. I've got Excel on order.

Thanks

 

Antbug: thanks!

I'd prefer not to raise the lights, since I sit next to it and don't want the glare. Taking out 2 bulbs is a good idea. I might try a much shorter photoperiod, say, 5 - 6 hours (it had been 12 hrs.).

 

The 4-bulb T-5 puts out about 216 watts, which is about 2.4 watts/gallon. It's my understanding that that's not unreasonable. I DO have issues with "pearling mist" and would prefer a totally crystal-clear tank, so the lower light level would help in that regard.

 

The T-5 fixture is directly on top of the tank. The bulbs are approx 2 inches or less from the water surface.

 

It does appear that my lighting is excessive, and I also found this interesting lighting-related thread: .

So I can either take out 2 bulbs as Antbug suggested or lower my photoperiod to 4-5 hours or so. If I lower the photoperiod, (which I'd prefer to do) I suspect I run the risk of rapidly depleting the plant-available CO2 and inviting another BBA outbreak, especially in areas of lower water flow. I guess I'll try the 2-bulb approach and see how things go. I've got some Excel on order, and I'll treat all the Anubias and crypts, make everything pristine and try again.