Yup... both threads I linked are examples of no co2
The first linked thread has a post from the OP that says:
Originally Posted by samamorgan
Well it's a low tech tank with no dosing or co2
, so growth rates have been pretty much as expected, nice and slow. Things are growing slightly faster than the previous fixture, though. Also one big difference is the growth is more compact and dense. My stargrass would reach to the top of my tank within a week and a half before, with large distances between nodes. Now it grows fairly compact and the leaves are broader and longer. Obviously getting much more light.
And in the second linked thread, the OP is quoted as saying...
Originally Posted by h2oaggie
No plans at all for CO2
or excel. Parva is doing well it just grows SO slow..
Although... I still think the addition of some ferts, excel and/or co2
(albeit DIY) would improve growth to some degree...