Reddit mentions of Rhinox Nano CO2 Diffuser - Keeps Aquarium Plants Healthy with CO2 Injection - 3-Minutes to Setup - Works Best with Pressurized CO2 Tank - for Tank Size Under 20 Gallon

I would recommend just going ahead and getting a regulator for the CO2. I tried DIY for a few months and it was always a pain and messy.. not to mention it looked gaudy.

Grab a Aquatek regulator (mini or normal) and a paintball tank from your local sporting goods store (Dick's or Academy). I personally don't know if you'd need one or two regulators and tanks since its a 20 long. I've only dealt with 10g and lower using CO2.

Anyways that's my take, I'm no expert and I don't know your budget but that should be less than $100 a tank / regulator.

As for the other stuff, I don't know sorry :(.

Edit: For diffusion methods get one of these bad boys: https://www.amazon.com/gp/product/B0058XWDFO/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1

I have a DIY I built from googling for my 15g. It is a constant pain in the ass to get the mixtures right for given surface agitation and bioload. And then every time you want to make a change, you have to wait a day for the mixture to restart. And if you are using CO2 to lower pH, this causes wild pH swings. And, you can't turn it off at night.

Save yourself pain and buy a real setup:

http://www.amazon.com/gp/aw/d/B001DTNWF2?pc_redir=1407847266&robot_redir=1

http://www.amazon.com/gp/aw/d/B0058XWDFO/ref=pd_aw_sims_5?pi=SL500_SS115&simLd=1

http://www.amazon.com/gp/aw/d/B0085282UK/ref=pd_aw_sims_2?pi=SY115&simLd=1

http://www.amazon.com/gp/aw/d/B008UCOFJW/ref=pd_aw_sims_1?pi=SY115&simLd=1

$175 with prime.

EDIT: Jesus I totally forgot about the leaks. Constant leaks in the DIY system. I had several seals give after several weeks of use. So you are never safe. I think I currently have zip ties holding my overflow lines together.

My only guess would be something like this: https://www.amazon.com/Rhinox-Nano-CO2-Diffuser-Pressurized/dp/B0058XWDFO/

That's about 1 x 2 inches. It's your basic diffuser - you'll get lots of micro bubbles, it's not the most efficient, but it should work.

The fluval CO2 system requires you to use disposable co2 canisters. The system comes in two sizes, 20 gram and 88 gram. Depending on the CO2 requirements of your plants, it could end up getting a tad expensive. You may be able to get away with it on such a small tank, but it the long run it may be cheaper to purchase a larger, refillable system.
Assuming you go with the 20 gram kit, which is recommended for up to 15gal. That's ~$28 + S&H. Assuming you are conservative with your CO2, You'll probably use 1 canister every 2 weeks. A 20 gram 3 pack is $14 + S&H. Over the course of a year you will spend ~$145 + S&H for CO2. Over 2 years, that number will be around ~$250 + a lot of S&H. Plus, if you decide to upgrade your tank, you'll also have to upgrade your CO2 system.
If you have the money to spend up front, you'll save yourself time and money in the long run. Get a 24oz Paintball CO2 tank from Amazon for $21. Get it filled at your local sporting goods store for ~$4. Get a diffuser from Amazon for ~$11. Then get a Paintball CO2 Regulator from GLA for $189. One fill up on your tank is equal to more than 34 20 gram canisters from Fluval and it only costs about $4 to refill, and if you have a Dicks Sporting Goods near you, 5th refill is free. Total cost is $221 + S&H, but that regulator is quality made and will last you years.
This is the set-up I use on my 7.5 gal and I'll be honest, after all other methods of "low cost" CO2 injection failed me and wasted my money, shelling out $200 for a regulator was quite painful, but this was the single best purchase I've ever made in my 20 years of keeping fish. So, if you can afford it, or can wait a bit and save some cash, it's worth it.
The simple fact that Fluval wants to charge you 13.99 for just over 2.1 ounces of CO2 when you can get a 24oz tank filled for $4 should make you question the purchase of their system.

Hey I just bought the same tank! I fit the same exact heater in the compartment next to the filter intake tube, it fit perfectly. I also used a little over half a bag of eco-complete. I just planted it a couple days ago. I bought a Nutrafin co2 kit but the ladder diffuser/bubble counter took up a whole wall so I ditched it and bought this glass diffuser and this bubble counter, they're still in the mail though so can't comment on how they work.

It looks like you're going with pressurized co2 which I sort of want to too but the replacement tanks seem expensive. Kind of wish I hadn't bought the Nutrafin and just made my own bottle DIY but the cannister is nice and so is the tubing it comes with and I'll just use the ladder diffuser on a bigger tank. There's not much room to work with and the lid seems annoying to fit things under, like tubing so I'm still working on that but overall it's a beautiful tank. Good luck!

I use disposable pressurized co2 canisters right now with one of these:

http://www.amazon.com/Nano-CO2-Diffuser-Reactor-Aquarium/dp/B0058XWDFO/

this is what you're using, right?

http://www.amazon.com/Fluval-Ceramic-88g-CO2-Diffuser-Ounces/dp/B004GCO35G

& I already have the fluval bubble counter!

If you have a hydroponics store nearby, a lot of them do CO2 tank rentals. It works like propane rentals, you put a deposit on an initial (full) tank and you pay to switch them out when you are empty. If you ever drop CO2 or need your money back, you just return the tank for your deposit.

For a regulator, I recommend going with a full regulator. Even if you ultimately go with a paintball sized canister, you can use an adapter to go down. While you can get an adapter to go the other way (paintball regulator on a full tank), it's much more limiting on the future. The Aquatek regulators are hit or miss (some people love them, some hate them), but I haven't had a problem with mine, and it was by far the cheapest option. GLA regulators are a work of art but much harder on the budget.

Aquatek regulators come with an integrated bubble counter and check valve, but you can use any check valves including the dollar ones at any pet store. Bubble counters are relatively cheap, but if you end up using a ceramic diffuser most have a bubble counter built in. You can get cheap ceramic diffusers on Amazon.

If you run a canister, I'd recommend just getting an Ista reactor. It's not much more money, it's less maintenance than cleaning diffusers, there's less CO2 lost, and less clutter in your tank. If have a canister you want to go something more sleek, you can get an in-line atomizer but I believe these require occasional maintenance compared to a reactor.

I've got a paintball tank with this cheapo regulator. I'll spend a bit more on a nicer one someday, but for now it gets the job done. The diffuser is a cheap glass one with a ceramic disk in it. A lot of the reviews mentioned it being overly fragile, but it's been a tough little sucker for me.

I am like you, and have done DIY until very recently. Spend the money. You won't regret the purchase. I was only slightly over 100 bucks on mine, but it was worth every penny to be rid of the hassle. The only issue with the valve I'll recommend is that you can't go over 1500 PSI even though the bottle I'll recommend is rated for 1800. Make sure to mention that when you get the bottle filled. The regulator is only rated at 1500. Here is what I bought.

CO2 Regulator
CO2 Tank
CO2 Diffuser

So yea, some tips. Don't fill tank over 1500 PSI. Make sure green knob is all the way in off position and it's not plugged in when you screw on the regulator. Screw on the regulator ALL THE WAY. Plug regulator in, slowly open the green knob. This assumes you have all the tubing hooked up. The bubble counter is super handy :) It only costs me 5 dollars to fill up the tank at Dicks sporting goods store. So after the upfront cost, I can run multiple tanks with a splitter off this, for a 5 dollar every few months fee. Totally worth it for the consistent bubbles and lack of hassle from DIY. If you get a timer, you can plug your regulator and light into it and you can control when the CO2 and light come on. You just need to trust us man, 130 bucks for this is worth it... so worth it. The bubble counter comes in the regulator I linked. The only things you'll need to buy other than what I posted for a 100% system is silicon tubing to link it all up, and maybe some suction cups. I didn't list this because that's a few dollars at most on Amazon. Don't listen to the 300 dollar crowd, my system is sub 150 and works just as well as theirs.

Would highly recommend a system.

Sure! I had started a thread here when I was buying my parts.

• CO2 Regulator
  
  
• 20oz CO2 Tank
  
  
• CO2 Diffuser

I ordered this one. It didn't come with a suction cup, for one, which was a pain. Also, it only seemed to emit bubbles from a tiny portion of the surface area of the disc; one little corner was emitting bubbles while the rest were silent. I have had much better luck with the GLA atomic diffuser that I purchased.

I got it off amazon

Rhinox Nano CO2 Diffuser - https://www.amazon.com/dp/B0058XWDFO/ref=cm_sw_r_cp_apa_E-N8BbVBCYAE0

This is what I've got going on.

I bought this cap/hose system

This diffuser

You don't absolutely need a bubble counter but you could buy one if you want to be more precise. Also, the cap/hose thing allows for an easy and simple set up.

Finally getting around to installing a CO2 system in my established, planted 45g community tank. The tank is mainly comprised of mosses, dwarf hair grass, tall hair grass, crypts, and a few java plants. I've had problems with black beard algae so I adjusted my light regimen and treated it with H2O2 until it was gone. Now I'm getting growths of green algae, so at this point I'm ready to install a DIY paintball CO2 system to combat the algae, so I can use my lights to their full potential, and to increase plant growth. The parts listed below are my starting point, let me know your thoughts...

Milwaukee MA957 Regulator

Adapter

CO2 Hose--Couldn't find a clear one in 3/16ID

Diffuser

Drop Checker

Check Valve

Timer

For a total of $141 before tax

What is your opinion on this setup?


Additionally I think my Aquaclear 110 is on its last leg so and I'm looking to convert to a canister filter (one that won't break the bank). Should I go with the SunSun HW304B or the SunSun HW704B