Sorry to hear you cannot afford the 20" x 4.5" housing. I think you may run into problems with keeping your CO2 levels up using a sump and only running a 10" x 2.5" housing. I hope I am wrong but I've seen others not be able to do it.

Oh, if you think planted tanks are expensive, you definitely do not want to know the costs involved in reef keeping! :-)

Agree with above.

You definitely want a 20" filter housing for a tank that size. You'll never get the results you want with the smaller housing.

It that's a deal breaker, you might not be prepared for the costs involved a planted tank. Not saying that to be rude, just being truthful.

It may not be reef expensive, but believe me it adds up. And if there is one thing I have learned, do it right the first time. Cheap usually = replacing it down the road and even more cost.

If I were you, I wouldn't give much credence to Youtubers. Get to know some successful folks with similar sized tanks to yours, and pick their brains. They will guide you with practical experience.

Good luck and look forward to seeing what you come up with.

Ok, I was worried about that. I dont really plan on putting in an additional filter because the purpose is for CO2. The 2.5vs4.5 is only the filter ring size, not the actual width of the housing itself (as previously mentioned by another user. Thank you). So im thinking just getting a 20"x2.5".

Sent from my SM-A215U1 using Tapatalk

Jeffkrol - thank you so much - I've
had a hard time getting good info on Co2 with sums and straight answers.

Jellopuddingpop - question for you as you've clearly got a lot of practical experience on this...How do you plumb a reactor in the sump? Detail - .I have a 180gallon waterbox with a 40gallin sump - have done an initial heavy planting - looking at dual stage regulator from CO2AIR - their recommendation on a diffuser vs a reactor has been vague despite 2 emails with specific questions. Sounds like you'd recommend a reactor - can you explain how id plumb a reactor in a sump, or share a link? Many thanks! Appreciate your help, newbie here to “real” planted tanks.

don't assume, that is why a lot of people picking the 20X 2.5 thinking it is more efficient than the 10X 4.5.

Yup. I checked the dimensions, the housing itself is 20"x5"x5"

Sent from my SM-A215U1 using Tapatalk

compare it is inner diameter of the case, where the threads at, it is also the wildest position.

correction:
ehh, actually, compare the inner diameter at the middle of the shell case.




see the difference? anyway, 20X2.5 is fine as long as it works well for your planted tank, ...

i'm new here and genuinely curious...

i see plenty of people noting they use 20" housings for diy cerges reactors - are any/many/most using the 20x4.5? having the 2.5" cartridge versions and seeing how big they are, and looking at that picture^, they must be truly massive!

how big the filter housing to choose, depends on the water flow rate and the size of your planted tank.

as I said, 20 X 2.5 is fine if it works well, what I want to make clear here is the 10 X 4.5 is more efficient than the 20 X 2.5 for co2 diffusion, so if you can pick the 4.5 diameter and it is best to avoid 2.5, and of course, the best is 20 X 4.5 if it is needed for a large planted tank.

add:
20x4.5 or 10x4.5 is not big, it is big if the planted tank it works with is normal size.

I've used this exact build on an FX5 with no problems. Black tubing inside the filter is just 1" corrugated pond tubing cut to size. I'd recommend this type of reactor for your 125g tank. You can also split a line before and after the reactor with a ball valve on the other line to control how much flow goes into the reactor if for whatever reason it is too much. This build was about $30 total:

Clear 10" filter housing with 3/4" ports - $20 on eBay
3/4" PVC nipple - $0.78 from PVC Fittings Online
3/4" FPT Tee - $1.41
3/4" x 1/4" reducer MPT x FPT - $0.60
3/4" Barb x MPT adapter - (2) $1.62
1/4" MPT x 3/16" barb brass fitting - $5 at Home Depot

So what actually breaks up the CO2 bubbles in something like this? I'm asking because I pick up a system tomorrow that I am putting on my 180 gal and Something like this would work better I think.

CO2 will simply dissolve in water, as long as there is enough surface area of the gas bubbles (diffuser), or there is something that keep the bubble tumbling in current (reactor). The purpose of this discussion is that there needs to be the correct amount of water flow for the amount of CO2 you're injecting. Too much flow, and the water pushes the bubbles out of the reactor. To little flow, and the bubbles gather into a pocket at the top of the reactor.

Oh sweet. Thanks for the detailed build explanation. I was looking for where to find the adapter for the co2 tubing cause i couldn't find the name of it. My housing should come in tomorrow. Amazon said the dimensions were 20x4.5, but the photos looks kinda sketch. If it's not, then I'll have to return it.

Sent from my SM-A215U1 using Tapatalk

From what I've seen, people fill up the housing a type of media of their choosing. I plan on taking a sponge that ill cut to size for a disk or two, and then fill the rest of the housing with small lava rocks. Im gonna try about 1/3 sponge and 2/3 lava rock.

Sent from my SM-A215U1 using Tapatalk