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Balancing for Plants and Fish, O2 and CO2

797 Views 8 Replies 6 Participants Last post by  Zorfox
Hi everyone,

I've been adjusting my setup based on your fantastic feedback to other questions.

I've been advised the following:
  • Keep my lights on for about 6hrs a day, this to help reduce algae
  • Run my CO2 only while the lights are on.
  • Maintain some agitation to allow O2 gas exchange but keep CO2 while lights are on.
  • Run airstone at night, to improve O2 gas exchange since plants will now be consuming O2 and competing with the fish for it.

My setup is:
  • 7.5 GAL tank (Mr. Aqua Bowfront)
  • Pressurized CO2
  • Fish: 1 Betta, 1 Longfin Albino Bushynose pleco, 4 rasboras
  • Plants: A few little patches of Baby Dwarf Tears, 2 anubias, 5 branches of Ludwigia Repens, and trying to build a XMas moss wall

So far everything seems to be good, 0 Ammonia, 0 Nitrites, 5ppm Nitrates.

However the Ludwigia seems to not be doing so great, it is not the pretty red it was when I got it, it doesn't seem like dying, but it feels like it is struggling.

So, I have two questions:
A) Is there anything I could do to help the Ludwigia go back to that nice bright red.
B) During the day, with no artificial light on, are the plants photosynthesizing?

Thank you so much for being very helpful.
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It takes a certain amount of energy for the plants to photosynthesize. If the tank light is off and the tank is not near a window then there is probably not enough energy reaching the plant leaves for them to photosynthesize.

I would try increasing the time the light is on, perhaps going to 6.5 or 7 hour per day for a week and see what happens.

Hope you have a larger tank in the near future. Bristlenose Plecs need a much larger tank than yours.
Thanks for your reply Diana.
So, if there is not enough energy, then does that mean that the plants are virtually in Night Mode consuming O2 and producing CO2?

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I would have the co2 come on maybe 15 minutes or so before the light come on and have it shut off 15 minutes of so before lights out.
Plants respond well with lengthy lighting hours, but that comes with a price too, algae. My tank gets indirect sunlight but I can tell they don't photosynthesize because the leaves folded once tank lights are off. I use to have my lights for 8 hours with good growth but had some algae. Now I have them on for 5 hours and ambience light thereafter, even BBA starts to go away. I've rather have slow growth, less algae and less trimming. You don't need airstone as long as there's surface agitation from your main filter.
First thing I'd suggest is get some Seachem Iron and see what happens after a few weeks. I started supplementing my micro ferts with iron and noticed that my Rotala's new leaves were much redder than they had previously been.
Tom Barr suggests promoting red colouring through limiting both light and NO3 but I haven't consciously tried that. However my Wisteria may be making that happen as I've read it is a hog on nitrate.
I was looking into the Seachem products, would you say use only Iron, or get the all rounded Flourish?

Thank you everyone for your awesome responses.
I made the assumption you were already dosing ferts and the iron was just supplemental. If you are not dosing ferts now but are running with high light and CO2 your soon going to have some problems. Here are some threads to help with that.
I didn't see fertilizers listed. All the light and CO2 in the world won't help if plants are limited by nutrients. A nitrate of 5ppm is pretty low. Consider EI dosing with dry ferts. Leave the Seachem products for the rich. There is no need to pay money for water.

Here is dosing information for various sized tanks. Here is a primer to non-limiting nutrient dosing.

There are plenty of places online to purchase dry fertilizers. A member here, Nilocg, sales them as cheap as you'll find and has great support.
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