?Short-term CO2 boost in low-tech tank?

[Fletch]

So I have a low-tech 33gal tank with modest amounts of Java miss, Java fern, cabomba, Blyxa, Lillaeopsis, and Rotala rotundifolia. The plants have mostly been added in the last 3 weeks and are growing slowly in what I would say is medium light (1 Aquaray Grobeam 600 for 8 hrs/day).
I don't want to be tied to CO2 because the low-maintenance aspect of a low-tech tank is important to me.
My question is: in the interest of getting the tank grown in faster, what might be the pros and cons of running a primitive DIY CO2 system for a couple months or until plant growth/coverage is adequate, and then switching back to low-tech?
Btw the tank is about 100% stocked according to aqadvisor. I have an AC70 which provides a huge amount of flow. Nitrates are usually in the 30-40 ppm range with weekly water changes of 30-50%.
Thanks for any help people!

[lucius]

You can try liquid carbon, Seachem's Flourish Excel.  That's what I started with and still dose with it every couple of days for algae control.

[charlie]

Hi Fletch,in my opinion you are better off getting more plant mass in there as opposed to waiting for it to grow in even with your plan of short term use of CO2.
As with any planted tank, it is highly recommended to start the tank with a good plant mass, the reasoning is , if your tank is new & sparingly planted you are running a higher risk of being troubled with algae issues, since there is not enough plants to use up the possible available nutrients.
One thing that jumps out at me  is your Nitrate levels of 30-40 ppm, if you are adding Nitrates, you need to cut back the nitrate. If you are not adding Nitrates , then the question becomes where is the Nitrates coming from - possibly ' over feeding"? for now you may want to target 10-15 ppm of Nitrate - frequent large water changes to get it down.
Grobeam +modest plant mass + mostly slow growing plants  with 30-40 ppms of nitrate = the greater chance of algae issues.
Regards
P.S. as mentioned Excel is a benefit but is not as good as CO2.

[wolfiewill]

I completely agree with charlie. You absolutely must max out the plant biomass, precisely for the reasons he stated. The short term use of CO2 will work but you'll loose some of your species when you stop. And you won't know which ones will die until you do (I'd guess but that's not productive; but some of your species certainly will not survive the transition).

And I use the GroBeam 600s in many of my tanks and I would think by using them you certainly have a leg up on controlling algae, but several of your plant species will need more light than that. I suggest you get a second GroBeam 600 asap.

And I also agree with charlie also about the nitrate levels. I have a 25 gallon tank with two GroBeam 600s, no CO2, daily Exel only (at twice the recommended dosage), no macros, Fluval Stratum substrate over Flourite red, which at the moment is over stocked with fish, and I do a 55% plus water change weekly if the nitrate level exceeds 5 ppm. I have no algae but I also have negligible phosphate levels (~0.2 ppm or less). The lights were on 13 hours per day without problems, but I reduced the lights-on period to 11 hours so I wouldn't have to clean the glass. It works with Cryptocoryne species, Staurygns repens, Crimum calimistratum, Silvania, and a little Java moss.

The bottom line here is without CO2 and more light, it's going to be hard to do what you want to do without algae issues.

[exv152]

Another option that often gets overlooked as a viable low tech approach is to use mineralized top soil with a cap.  The soil will provide its own source of carbon, and you can get away with med intensity light.  Because to add co2 then take it away is really going to encourage algae. Low & fluctuating co2 is often blamed for some of the tougher algaes to get rid of. But I would definitely increase plant biomass no matter what you choose.

[Fletch]

Thanks everyone. All very helpful info!
It sounds like the bottom line is that I need more plants. However, I don't really think I have algae problems at this point. Basically, I need to scrub the glass off every 2 weeks but it isn't too bad - although I have got some brown (diatom) stuff on the gravel in the last few weeks. I got a couple Otos last week though and they have started doing their job.
I do notice, though, that the water has a subtle green hue to it. This is more obvious if I remove some water (eg in a white yogurt container). Does this constitute "algae issues"? I don't know . . . it doesn't really bother me too much.
As for the nitrates, I am definitely not adding any fertilizers at this point. So it is pretty much coming from fish waste. I wouldn't say there is much uneaten food, as it is almost impossible for me to get any pellets to actually hit the bottom for my Cories (the lemon tetras and zebras devour everything as it sinks). So I put a couple Hikari bottom feeder pellets in at night for them.
However, I may well be overfeeding. I feed them twice a day, and each time the food is eaten in about 30 seconds. It is the New Life Spectrum small fish formula pellets. To me, this doesn't seem like a lot of food given the number of fish, but maybe that is the real issue -- the bioload of all those fish (26 in all)?
It's good to know that changing the levels of CO2 isn't going to be helpful. I guess I'll just tolerate the slow growth and see if I can find some more plants. Any suggestions on fast-growing ones that are cheap? I'm a bit concerned about introducing disease or pests . . .
Getting more light is not an option for me at this point for budgetary reasons, so I'm sticking with what I've got. If some of the plants don't make it, well, I'm considering it all as a kind of experiment anyway . . .

[exv152]

I do notice, though, that the water has a subtle green hue to it. This is more obvious if I remove some water (eg in a white yogurt container). Does this constitute "algae issues"? I don't know . . . it doesn't really bother me too much.
As for the nitrates, I am definitely not adding any fertilizers at this point. So it is pretty much coming from fish waste. I wouldn't say there is much uneaten food, as it is almost impossible for me to get any pellets to actually hit the bottom for my Cories (the lemon tetras and zebras devour everything as it sinks). So I put a couple Hikari bottom feeder pellets in at night for them.
However, I may well be overfeeding. I feed them twice a day, and each time the food is eaten in about 30 seconds. It is the New Life Spectrum small fish formula pellets. To me, this doesn't seem like a lot of food given the number of fish, but maybe that is the real issue -- the bioload of all those fish (26 in all)?
It's good to know that changing the levels of CO2 isn't going to be helpful. I guess I'll just tolerate the slow growth and see if I can find some more plants. Any suggestions on fast-growing ones that are cheap? I'm a bit concerned about introducing disease or pests . . .
Getting more light is not an option for me at this point for budgetary reasons, so I'm sticking with what I've got. If some of the plants don't make it, well, I'm considering it all as a kind of experiment anyway . . .

Green water algae and high nitrates would definitely be indicators of a high fish bioload. I would reduce feeding to once a day, and even skip a day once or twice a week, and consider reducing the number of fish if possible. For fast growing easy low light plants, try any type of hygrophila, especially the polysperma and difformis variety, they grows like weeds. Also, cryps, anubias, mosses, bacopa, swords (echinodorus), java ferns, sagittaria, vals, they grow a bit slower but are easy to maintain.

[lucius]

try any type of hygrophila, especially the polysperma and difformis variety, they grows like weeds.

+1.  I use to throw out buckets of water wisteria and water sprite weekly because it grew so fast.