What's the effect of high co2 + low Par?

[snowballs99]

Do the leaves stay greener?
Is co2 most responsible for leaf size?
Does growth rate really slow down much?
Do stems get thinner?

Haven't seen many set ups with very low light (20-30 par) but with high co2.

 

[Yugang]

The conventional wisdom in the hobby is that light drives the growth rate of plants, and that we want to avoid deficiencies of nutrients, including CO2, necessary to support that growth.

I believe that high CO2 and low PAR will be ok for the plants, and probably not much different from lower CO2 at that same low light.

We may caution for health of livestock, as the low light may lead to lower O2 in the tank. Critters have a higher tolerance for CO2 with higher O2, so there may be an increased risk gassing the fish in this setup.

I am personally not sure what the benefit of this setup would be.

 

[Pepere]

Haven't seen many set ups with very low light (20-30 par) but with high co2.

The biggest downside I would guess would be unnecessary expense of co2 that just isnt being utilized due to low PAR.

Yugangs concern though about low oxygen levels is a reasonable guess as well.

In my 20 high basement quarantine tank,I instituted a sugar gelatine reactor keeping some co2 bells filled with co2 and manage to keep around 13 ppm co2 in the water…. I have gotten meaningful improvement of growth from that relatively low injection rate..

 

[Naturescapes_Rocco]

"Good" CO2 would be a better term rather than "high".

Plants that need 40-50ppm CO2 like Erio quin also need high light, too, so they wouldn't work in this setup.

Agreed with Yugang; light is what sets the "Target pace" for your little cell factories (plants). If you can't keep up with the "pace" in terms of providing CO2, Macros, and Micros, your plants will suffer and get algae.

Low light and good CO2 (20-30ppm) is a solid combination for many easy plants like java fern, anubias, rotalas, ludwigias, etc. because you won't need to worry about whether you're providing enough CO2 relative to your light strength.

In my low tech bowl, there's less than 10ppm CO2 at the daily peak, if not even less. I grow lots of the same plants I grow in my high tech tanks, but I use a much weaker light on the bowl because without CO2, I can't keep up with the "pace" a stronger light sets. All about balance!

 

[snowballs99]

Does erios actually need high light tho?

I've grown an entire tank filled with eriocaulon ratnigir with a 10 watt light, buried under duckweed, and then floating moss on top of that.

I think so few of us run low light with good co2 that it's surprising that a lot of "high light plants" just kinda suck at getting co2 so we need higher lighting to compensate.

 

[snowballs99]

The biggest downside I would guess would be unnecessary expense of co2 that just isnt being utilized due to low PAR.

Yugangs concern though about low oxygen levels is a reasonable guess as well.

In my 20 high basement quarantine tank,I instituted a sugar gelatine reactor keeping some co2 bells filled with co2 and manage to keep around 13 ppm co2 in the water…. I have gotten meaningful improvement of growth from that relatively low injection rate..

What if the benefit of it is that we can run relatively high EI levels of nutrients with minimum algae risk and less water changes? Much longer photoperiods etc.

To be fair my experience so far is nutrient spikes will cause algae pretty much no matter what lol.

I'm kinda more curious what happens to plant growth forms to be honest.