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Lights, Ferts, Algae, and how they relate?

1K views 8 replies 5 participants last post by  Hoppy 
#1 ·
I lowered my lights 2". That's about 20" off the substrate on a 12" tank. I have been dosing "1/4"EI - 1/4 NPK on Saturday and 1/4 CSM+B on Sunday, 50% water change weekly.

It has been over a week since I lowered the lights and I am starting to see some green algae on parts of the glass. Not the kind of algae that are destructive to plants - nice algae. Oh and I took out a large Ruffled Sword and some Crypt Wendtii whose leaves were touching the water surface over the past couple of weeks.

About that algae, if I add 1/4 NPK on Wednesdays, Day 5, would it put me in the right direction with dealing with the algae? Thanks.

The one thing I worry about is CO2 if the light gets too strong.
 
#3 ·
Based on Tom Barr's concepts:

Light and CO2 need to be in balance. Get the CO2 right. About 30 ppm is a good level for a planted tank with fish. A tiny bit higher is usually OK, but go by the fish.

All the other ferts should be provided in enough supply that there is no possibility of shortage. Dosing only 1/4 of the recipe once a week is a shortage of ferts. You are only dosing 1/12 of the right amount. That may be OK in a low tech tank. What is the NO3 test showing?
Fish food can supply some nutrients, but is rather low in some.
Potassium, Iron and Calcium are the lowest items in fish food. Water with a GH of at least 3 dGH is usually OK for calcium, but I would dose higher amounts of K (use K2SO4 if you do not want much NO3) and chelated iron.
 
#4 ·
I have a low-tech planted tank. That's why I'm a little concerned about CO2 being enough as I increase the light intensity. That's also why I'm doing 1/4 IE. I wonder if the algae shows up when the CO2 gets too low at some point during the photosynthesis time and the plants stop working or work slower, leaving nutrients and light for the algae. Maybe I should just reduce the intensity to what it was before the algae started up. I will also add the second dose per week of NPK in case I don't have enough of it.

NO3 is 20-30ppm. pH had dropped down to 6.6 from 7.6. I'm having trouble with reading the GH test - looks like over 7 dGH. KH is 3ppm.

I'd appreciate any advice or comments. Thanks.
 
#5 ·
When lowering the lights your are directly intensifying the light that the plants get. this will drive faster growth (more light = plants want to grow), problem is not your ferts but rather the available co2. The demand for ferts would be small at that point but co2 demand is far greater and is probably the cause for the algae showing up.

I have been dialling my 75g low tech since the beginning and I am 99% algae free and have been for a long time. but if I lower my lights about 1.5" i start to see green spot algae on glass and anubias. and it shows up quick, within a week or so.

I would suggest raising the lights back up and if anything you can extend the photoperiod an hour and watch to see what happens. I find that extending an hour is far less of a change compared to a 2" drop. once plant mass increases you can consider lowering it again and maybe only 1" at a time.

Another thing to keep in mind is that you should be waiting about 2-3 weeks after making a change before trying to changing something else. It will allow the tank to adjust and you will be able to see the results through your plants.

your tank looks very bright to me from the avatar pics.
 
#6 ·
Thanks. I have been thinking a lot about this. I put the lights back up 2" to see if the algae is reduced.

We know that the supply of CO2 in a low-tech tank is not very much to start out with. Something I read made me wonder about the period of time during the photoperiod when CO2 becomes very scarce. The plants must shut down and photosythesis must not be able to occur. I'm wondering if that really opens the gate for algae, when the plants aren't running.

I already extended the photoperiod an hour from 12-7 to 12-8, and I got the same kind of algae, so I set it back. I could try again once 2-3 weeks have gone by or the algae is gone.

The tank is very light. A stem plant that I don't have the name for has been growing pretty fast. I guess you could call this microdialing in.
 
#7 ·
Some people turn the lights off for an hour or two mid day. This allows the CO2 to build back up and the plants can get going again in the afternoon.

I did this for several years, but in the summer only. My goal was temperature control.
I would turn off the lights when it started getting hot, and this did moderate the temperature in the tanks.
The first year I noticed less algae. The next year I do not know if there was less algae or the same amount.

To follow up on this you can search using the term Siesta.
 
#8 ·
Thanks for the tip Diana.

Here's a quick shot of my tank as it stands, minus the Ruffled Sword and Crypts. Yeah, I shoulda cleaned the glass. Most of the brown stuff on the bottom is planting mix. I just bought a turkey baster to try to get rid of some of it.

Steven
 

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#9 ·
Light drives the growth of both plants and algae. For reasons I don't understand, when the plants are growing in good health, as fast as the light can make them grow, algae tends to not start growing. Also, with more than low light, if the availability of carbon for the plants is different from day to day, one specific algae, BBA, tends to start growing, and once started, tends to keep growing. But, excessive fertilizing has not been demonstrated to cause algae to grow. That's why the EI fertilizing method can work so well.
 
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