[burr740]

CO2 will help plants cope with low light/low nutrient situations. Plants spend a lot of resources (energy) gathering CO2 when it is in short supply. Google rubisco.

Having ample co2 allows plants to allocate their resources to better utilize limited light and nutrients. Low light tanks will greatly benefit from having co2. That is why you saw immediate results from Excel.

However, if one or more required nutrients is totally absent, the only way to solve that is by adding the missing nutrient(s).

 

[burr740]

You're going to need a full range of nutrients either way you go. Might get by with fish poop and tap water, or you may need to supply additional compounds.

That all depends on the light levels and what kind of plants you have, also how many plants, fish, etc. Your plants can answer this better than anyone on a mssg board.

What you saw from using Excel is just a small example of what real co2 would do, a very small example.

I'd stay away from diy unless you know what you are doing and really have a good set up, and are diligent about maintaining it. It is very difficult to keep diy running consistently. Up and down co2 levels from one day to the next will grow more algae than plants.

Many people make the mistake of thinking DIY is the way to go...because they dont need much CO2 to begin with. The logic is sound, but keeping a steady rate is just as important as how much. That is where DIY fails more often than not.

You're better off in the long run making the initial investment in a good pressurized system that you can set and forget.

 

[burr740]

Well...it wont be long before you're well over $100 screwing around with any diy set up. And that's not counting the headaches that come with it. And I say this as someone who's ran several DIY systems successfully in the past on a few different tanks.

 

[burr740]

Even with very low light it's going to take a minimum 10-15 ppm of co2 to make any difference. That is simply not possible with 1 bubble every 4-5 seconds into a 75 gallon tank. 2-3 per second...maybe.

Seems like Excel might be the best way for you to go at this point. You've already seen positive results. The only drawback is cost, right?

Here is a gallon of the same thing for $26 + shipping. (comes in quarts too)

Amazon.com : Metrex Metricide Gallon 14 Day - Model 182337 - Each : Health And Personal Care : Beauty


It is cheaper and stronger than Excel. Approximately 6 ml of Metricide = 10 ml Excel. Both products are gluteraldehyde.

If you go this route, be sure to throw away the little packet of "activator" that comes with it. Ignore the instructions and dont use that. Just use the liquid same as you would Excel.