Who Gives A Fish Forums

I'm relatively new to planted tanks, having recently set up a 20-gallon long aquarium - my first fully stocked with live plants. It's been about 8 weeks since it was cycled and running, but unfortunately, my plants aren't exactly thriving.

My setup consists of a T5 high output dual lamp, with a 6700k and a 10,000k bulb. I'm using a Fluval 30 hang on the back filter and a smaller air pump with an anchored air stone, which is supposedly suitable for a 20-gallon tank, but doesn't create much water movement.

My substrate is about 1.5 inches of Flourite, topped with 0.5 inches of pool sand. I occasionally add CO2 booster and Flourish as the only chemicals.

I have a few questions: Am I dealing with diatoms, and if so, how do I get rid of them? Is my circulation sufficient, or should I add more to prevent plant matter from accumulating on the leaves? Are there any red flags in my setup that I should be aware of?

Any advice or guidance would be greatly appreciated.

Diatoms are typical in new tanks, they'll fade with time. Creating more flow with a small pump would be my approach. It can take a while for plants to establish themselves in a new setup. Once things balance out, you'll be in the clear.

If by "diatoms" you mean the brown algae that wipes off easily with your finger, then yeah, that's normal in new tanks, like motors said. But if you're referring to something else, I've had my own struggles with a diatom bloom in one of my tanks - cloudy water, brownish organics, the works.

Now, about your plant issues. The first thing that jumps out at me is the intense lighting. I'm gonna be blunt here - I think you need to dial it back, at least by half. Maybe try running just one tube light without the second, or look into a different fixture. The problem is, that intense light is driving photosynthesis, but your plants aren't getting the nutrients they need to keep up.

CO2 is a big part of this. With that much light, you'll never have enough CO2 to balance it out. Even if you reduce the light, you'll still need to supplement. But it's not just CO2 - your plants need other essential nutrients too. A comprehensive liquid fertilizer might be the way to go.

Personally, I wouldn't bother with diffused CO2 in a small tank like a 20g. And as for liquid carbon supplements like API CO2 Booster, I'd advise against using them in a tank with fish. That stuff's not good for them.

I'm using Flourish Comprehensive, I've heard it's the way to go for a beginner like me. I've been using it as directed, but I'm wondering if I should be adding more given my high lighting setup. I've also been adding a CO2 booster, but I'm not sure if it's necessary with the air stone running. I've been told that the air stone should provide enough oxygen for the plants until they start growing, at which point I can reassess my CO2 needs. Maybe I should dial back the lighting a bit and see if that helps the plants take off, then I can reintroduce the CO2 and full lighting later on.