Aquatic Plant Forum banner
1 - 5 of 5 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter · #1 ·
Ever since i started to use an air-driven sponge filter for filtration, the plants in my tank have done very poorly. This, i have learnt, has to do with the high oxygen content that the constant bubble stream gives rise to: it drives the Co2 off big time.

Can any of the veterans, who have kept fish with both plants and air driven sponges, kindly let me know what plants i can hope to grow now? even the vallisneria is dwarfed, my old stand by that i grew so well as a teenager two decades ago! the Aponogetons, cryoptocoryne tropica, even lily took a direct hit, paling, growing smaller, dying out.

Angels are such awesmome community creatures (within limits). i love them in planted tanks.

best wishes,
Romi
 

·
Registered
Joined
·
26 Posts
I'm pretty sure you could get Elodea/Egeria/Anacharis to grow under very high-oxygen/low CO2 conditions, especially if you have hard water/add some baking soda. Elodea has an alternate carbonate-based photosynthesis pathway, which allows it to extract carbon from the water and photosynthesize even when dissolved CO2 levels are low. I think there are a few other plants that have such an adaptation as well. All plants need carbon in order to live and grow; if there's no dissolved CO2 in the water, aquatic plants have to either make use of alternative carbon sources like carbonate ions, or send up leaves to the surface to allow direct gas exchange with the atmosphere. Your lily ought to be able to survive by doing the latter, unless it doesn't have enough starches stored in its rhizome to effectively reach the surface and start photosynthesizing.
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #3 ·
thanks for the response, 133tgeist. i remember reading about alternate carbon pathways in use in different plant species alright. the last in Diana Walstad's book. but the question is what are these plants that would rise above the O2 deficit and flourish with an air sponge filter. I did note your recommendation of elodea/anacharis/elodea, which is the same as what i guessed and that other poster (cannot see her anymore, wonder why? did i do something unintentionally?) also suggested. Please suggest more such species.

that water lily i mentioned had no floating leaves, just underwater ones. i wouldnt be interested in one with floating leaves coz i understand they reduce the surface area for fish dramatically.
 

·
Registered
Joined
·
26 Posts
Romi, among the other plants that use the bicarbonate pathway, ceratophylum and sagittaria come to mind, in addition to your vallisneria. If your val isn't growing either, perhaps there's not enough bicarbonate in the water for it to extract.

Also, you might need more light. Higher CO2 levels improve photosynthetic efficiency under low light, so that submerged plants in carbon-rich waters can sometimes survive under 1-4% of natural sunlight levels. This implies that in low-carbon situations, light use efficiency is reduced, so the plants need more light to photosynthesize when carbon is scarce. I know this runs counter to what people say about "light/CO2 balance", but that's referring to an optimal situation in which everything can be controlled. It's more efficient in many cases to add more CO2 than to add more light, that is, you'd get more benefit from increasing CO2 than from increasing light, hence light/CO2 balance. That's not the situation you have here.

In your situation, where there is little carbon, adding more light may enable your plants to use what's there more effectively. It won't be the most efficient solution (they'd grow better with more carbon and the same light) but it may work. I can't speak to potential effects on algal growth if you did this.

Also, an article on aquatic plant physiology over at The Krib suggests that the problem with plants getting enough CO2 under water does not have as much to do with its ability to be dissolved in water as its diffusibility in water. "Carbon dioxide dissolves readily in water. At air equilibrium, the concentration of CO2 in air and water is approximately equal at about 0.5 mg/L. Unfortunately, CO2 diffuses about ten thousand times slower in water than in air. This problem is compounded by the relatively thick unstirred layer (or Prandtl boundary) that surrounds aquatic plant leaves. The unstirred layer in aquatic plants is a layer of still water through which gases and nutrients must diffuse to reach the plant leaf. It is about 0.5 mm thick, which is ten times thicker than in terrestrial plants. The result is that approximately 30 mg/L free CO2 is required to saturate photosynthesis in submerged aquatic plants."

Note "still water". This suggests that water current (not surface agitation) might substantially improve CO2 uptake efficiency/plant growth by overcoming some of the diffusibility issues (a plant leaf using up all the CO2 in the immediate vicinity and having to wait for more to diffuse towards it from the surrounding water). Indeed, as an informal observation, many truly submersed aquatics tend to grow in moving water and have finely dissected leaves (think Cambomba, madascar lace plant, bolbitis etc) and many plants that grow in still water and have solid leaves try to throw up those leaves to the surface to take advantage of improved gas exchange and light conditions at the air/water boundary (Lilies, hygrophila polysperma, etc).

Presumably you're using a sponge filter because you don't want to use something that would promote more water movement; in this case, the only suggestions I can offer are to use more light, more carbonate hardness with bicarbonate-using plants, and to allow some plants to reach the surface. Your lily, which falls under the category of "still water plants adapted to reach the surface" will eventually die unless a) it is allowed to do so, or b) very high levels of light and dissolved CO2 are provided. It will use up all of the starch reserves in its rhizome attempting to reach the surface and replenish them, and then it will fade away. It sounds like it would be better off in a different tank.
 

·
Registered
Joined
·
287 Posts
or you could try dosing seachem excel. :D
I DO have to ask... any reason not to go back to the filtration system (non air driven)
you were using previously?
another good plant option is Java Moss/ Christmas moss/ flame moss....
Mine grows wonderfully in my low tech, low light, non dosed, non c02 shrimp tanks.
 
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top