CO2 in Brackish for Plants? (Figure 8 Puffer)

I am about to start setting up my new brackish tank and have been doing research on what kinds of plants can survive in it. I love aquarium plants and hope to avoid plastic plants if I can for my figure 8 puffer. I figured I would throw a post on here in case anyone has experience with this. It's hard to find discussions on brackish planted tanks, let alone any mentioning CO2.

So my question is, would it be a bad idea to inject CO2 in brackish to help grow plants and keep the algae away? I know it will lower the ph, so I am keeping that in mind and will be testing the water first once I get my substrate (aggregate sand) and rocks in place this week. I would have plenty of time to test my water before I place an order for the puffer. I am still trying to do research if having CO2 will have any negative effects on puffers (so far it looks fine unless it swings the ph too much). I would think the CO2 would help keep the plants alive and grow faster like it does with freshwater. I know plants in brackish tanks can be a challenge, so if CO2 will help that would be awesome.

This would be the set up if I decide to do CO2:
- CO2 during the day through diffuser on a solenoid timer
- Fluval 3.0 (already purchased for this tank with the original intention of doing freshwater planted. So I will use this regardless.)
- Liquid fertilizer (Thrive+, already using this on my other freshwater tanks.)
- Air stone on a timer to run at night, removing any excess CO2 and oxygenating the water.

If I did not go with CO2, I worry the algae will still be a problem and cover up my plants and block their light. But worst case I am willing to go without real plants if none of them end up working out. It would be hardly any extra effort for me to add CO2 since I already run it on my other tank, so unless I find out any negative side effects I think I will give it a shot.

On the off chance anyone reads this and has any advice, thank you in advance!

 

I don't see any reason why CO2 wouldn't help the plants, as long as the plants can handle the salt. With a brackish fish like figure 8s you have the added benefit of being able to use powerful pH buffers like aragonite to negate any swings.

What kind of plants are you wanting to keep?
That's the big question.

It's definitely possible to control algae in brackish without CO2, but the problem is that most plants grow slower in brackish in the first place so they're not removing as much nutrients from the water and your choices for "hungry" plants are limited.

I have succeeded in controlling algae in the past (low-tech) using water sprite, which is the only "hungry" plant that comes to mind for brackish. I had it growing floating so it got "free" CO2 and it grew like crazy. Perhaps injecting CO2 will get you a similar effect underwater.

 

I don't see any reason why CO2 wouldn't help the plants, as long as the plants can handle the salt. With a brackish fish like figure 8s you have the added benefit of being able to use powerful pH buffers like aragonite to negate any swings.

What kind of plants are you wanting to keep?
That's the big question.

It's definitely possible to control algae in brackish without CO2, but the problem is that most plants grow slower in brackish in the first place so they're not removing as much nutrients from the water and your choices for "hungry" plants are limited.

I have succeeded in controlling algae in the past (low-tech) using water sprite, which is the only "hungry" plant that comes to mind for brackish. I had it growing floating so it got "free" CO2 and it grew like crazy. Perhaps injecting CO2 will get you a similar effect underwater.

Thats been pretty much my thought too. I did some Googling and found the plants most people recommended, and also found this post: Planting Brackish Aquaria

So far I am considering these the most:
- Anacharis
- Cryptocoryne Wendtii
- Anubias Barteri
- Water sprite
- Vallisenria

I guess the only way to find out is just to give it a shot and see what happens. I expect you are right about finding the plants that grow faster so that it can actually make a difference in sucking up the nutrients. As opposed to having a bunch of low light slow growing plants only in there.

Another perk of my other freshwater CO2 tank is that I can try planting the clippings of various other plants I have, although I wouldn't expect them all to survive.

I am thinking I should only try out a few of the faster growing plants first, until the tank has balanced out (assuming they survive). After it gets past that first wave of algae (if there even is any), I can add in some various other plants like Crypts and anubias to see what I can make work and look nice. That way I don't waste money on some of the slower growers if they end up covered in algae and have no chance.

 

I vote for anacharis. I keep it in my 20 gallon brackish (F8 Puffer).

Let the algae grow and it will die back to a steady state that is easy to manage. If you try to remove it while it is growing you will fight it.

 

I vote for anacharis. I keep it in my 20 gallon brackish (F8 Puffer).

Let the algae grow and it will die back to a steady state that is easy to manage. If you try to remove it while it is growing you will fight it.

Awesome, and I love the look of it! Here is what I have decided to try first based on my research for brackish plants so far (and already have some of them planted now):

- Anacharis
- Water sprite
- Vallisenria
- Glossostigma elatinoides
- Subwassertang
- Micro sword lilaeopsis novaezelandiae
- Hygrophila corymbosa
- Tiger lotus

I plan to keep it freshwater while I am cycling the tank. Once the plants have been established, I will transition the water to the right brackish levels over time so that the plants and bacteria get acclimated slowly. After that I can finally add the puffer.

I am curious to see which plants will succeed or fail, but excited to find out and see how it goes!