No Machine Needed?


New Member
Mar 24, 2021
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Hey ya'll. I've recently been researching to start with some low light low maitenence plants. I read in an article that I could keep some plants that require less KH without any co2 machines by using Seachem's Flourish Exel Carbon Bioavailable. What are your thoughts and opinions? Has anybody used it before?


Jan 26, 2021
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Nanaimo, BC
I have used it with mixed success. It really seem to help with the amazon swords and the other Echinodorus plants but really set back my Java fern, Vals and Sags. For me I have decided to not use it any more. It is essentially a antiseptic and my research suggest if you do use it to be consistent on timing and dosage. If you do use it I would start with a half dose or less.

I have found it easier to grow plants in water with lower kH, and I wouldn't think for low light plants that you really would need additional carbon.

I essentially do not have enough kH (carbonate hardness) to measure in the test kits. I am having success with medium light (Nicrew G2), no C02, aquarium soil and growing the following plants (it has taken me about 4 months to get the proper light timing):

  • Lugwigia palustris (nice reddish stem plant)
  • Enchinodorus (the ones I am sure of listed below) (heavily rooted plants)
    • Echinodorus grisebachii
    • Echinodorus "Barthii" (hybrid)
    • Echinodorus "Ozelot green" (this has delicate leaves and the bristlenose has developed a taste for it)
  • Vallisneria sp (rooted plants but spread if happy via stolons)
  • Alternanthera reineckii 'Pink' (Stem plant, did poorly at first but after it was taller than 8" it started doing well)
  • Leptochilus pteropus (Java fern, attached to wood or free floating, tanks with this plant in them seem to be cleaner? than the others)
  • Staurogyne repens (but only in a shallow tank, seems to be a stem plant)
These plants are growing but not well or fast, it could be because my tank is 25" tall and it is hard to get light down to them without over lighting the upper section.
  • Sagittaria subulata (rooted plant spread with stolons? but slowly and sparsely)
  • Helanthium bolivianum (rooted plant spread with stolons? but slow growing, some have died, one has grown well)
Even with limited light I got the vals and java fern to grow.


Fish Guru
Jan 26, 2008
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Perth, WA
Don't use liquid CO2, it's bad for the fish.
Plants don't need additional CO2. there is plenty in the water from the fish, filter bacteria, and plants at night when they aren't photosynthesising. There is also CO2 in the air and that gets into the water.

When was the last time you saw plants in the wild taking up CO2, specifically provided to them by man? Never, because they don't need it. Plants don't need extra CO2. In fact recent research (from 2019/ 2020) has shown that terrestrial plants suffer when the CO2 levels go above normal levels. The same probably applies to aquatic plants, and extra CO2 is definitely bad for fish, shrimp and other aquatic organisms.

Can you put a second light unit above the tank or increase it somehow?
Good light and a bit of iron based aquarium plant fertiliser is all that is required to grow true aquatic plants in an aquarium.

Most plants that need CO2 and intense light and fertiliser are marsh or garden plants that are forced to grow underwater.

Java Moss and Java Fern do well in low light and with minimal nutrients.

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