What is this and what is wrong with it?

[Luna09]

Hey I have a 20 gallon tank with a 15 watt "all glass aquarium" bulb with a little symbol that is a circle with HG in the center.

I do not do CO2 injections because I am not sure what I am doing and I have yet to get to a wal-Mart or other store I can get the DIY materials.

My question is what type of plant is this and it there any way you could help me diagnose the problem.

The plant is growing like a lovely water weed, I'd say 2 cm a day. But in the mornings the top of it is browned. Once the light has been on for a few hours it perks back up, but for the most part the top 2" is lighter than the lower.

I thought I heard somewhere that plants switch to oxygen input at night so I thought maybe with everything else in the tank it was "suffocating/drowning" so I added an airstone for lights out with no avail. All my other plants are lovely, lush and growing inexorably.

Any helpful hints?

 

[Peyton]

That is bacopa caroliniana. Can't really tell by the pics as far as the lighter color. Plant's do tend to "color" up a bit as they get closer to the light source.

How long has the tank been running? The fact you have rotala wallichii (the pink needle leaf plant) growing in a non-co2 tank shows your doing something right.

 

[Luna09]

The tank has been cycled with fish since march so it is still very new. The funny thing is the rotala wallichii??? is doing the best other than my mini lily pad thing. Dwarf tiger lotus??? Maybe.

I have a feeling it has to do with pH to be honest. Because of the driftwood I have had a very hard time keeping my pH above 6.2. I'm assuming the rotala likes it acidic and the other doesn't. (this is 100% a hypothesis)

I've added crushed coral to try balancing things out but I am new to planted tanks so all of my thinking is strictly what I would call possibly common sense and beginners luck. I add a little bit of liquid API Leaf Zone once every week or so which seems to do no harm and I try very hard to keep up on WCs.

My 10 gallon on the other hand doesn't seem to grow as fast. I attribute that to the built in Marineland LEDs??