C02 Threshold?

[Slick Fork]

Just wondering if there were any general rules of thumb for when a C02 system becomes mandatory? I've got a 33g tank with just the standard 20w flourescent above it, and was thinking of upgrading to a 65w power compact fixture in the next month or so. This would put me at approximately 2wpg, would this be considered High or moderate lighting? I'm not sure I want to start messing around with CO2 just yet as the stories of ph swings make me a little nervous (still new to this whole thing)

In my tank I currently have a bunch of Java Moss and 2 Java Fern "Windelov". Is the lighting upgrade going to be overkill for low light plants like these?

Anyways, thanks in advance

Cheers!

 

[beviking]

My own general rule of thumb is when the plants look horrible (slightly bad = horrible to me) and/or algae is more predominant in the tank.

I inject CO2 and add ferts on one tank, I also have a 20gal with >40watts (they're 2-20watt bulbs overdriven by a larger ballast) that I do not use CO2 in. They're mostly slow growing plants in it as well. You can increase the plants growth rate to an extent, but there are limits as to how fast a given species will grow (given all factors optimal). Since your plants are also slow growers, I would suggest going w/o CO2 for now. Flourish Excel may not be a bad alternative for you either. It's an alternate carbon source in a liquid form. 2wpg is mid/moderate/medium light.
Best of luck.

 

[RTR]

I waffle a lot on that answer... I used to say ~2.5W/gal. NO, then I moved it down to ~2.0 W/gal. NO. Now I have several tanks at exactly 2W/gal NO in which I have to add carbon and other ferts or I get hair algae. PCs with decent reflectors are also brighter than the same wattage on NO tubes.

Java Moss and Java Fern can survive with low light, but they can handle a lot more than they are commonly given. But for that big a boost in lighting you are likely to want some faster growing plants just to eat the light.