[TheNewEra]

It doesn't matter as long as you are injecting enough CO2 into the water and there is enough flow throughout the tank to distribute the CO2 everywhere. I don't understand your concern about distributing the CO2 into the other filter (?)

Well that is kind of the question, though perhaps wrongly phrased. How does the flow and distribution of co2 go through the tank with the 2 filters?

As there will be an outlet on both the front and the back of the tank. All I am thinking of is if the co2 will get distributed evenly. The flow of the front outlet will, of course, lose some of its power by the time it reaches the outlet on the back. Does that mean that the 2nd filter picks up the flow of the first or will it create a "build up" zone of 2 competing flows where the co2 will get stuck?

Alternatively, am I just making this more difficult than it actually is? Am I placing the inlet and outlet on right places? This might seem rudimentary to some of the better, more experienced, scapers but it will be my first time working like this and I really just want to get it right.

I Have a 55 gallon and a 75 gallon in my office, I run two filters on each one. I have them setup just the way you described. I really like the setup as I get good surface agitation and a lot of filtration with two filters. I use an Eheim pro 4 250 on most all my tanks. The 55 Gallon has one reactor and one CO2 setup I get a 1.0 PH drop and everything is growing well so I assume I have good distribution of CO2 for my purposes. The 75 Gallon has two reactors and two CO2 setups, this is really overkill for the size of tank the only reason I did it was because I had the equipment, and I don't have to change the CO2 tanks out as often. A 120P is a great tank good luck with your build.

The first picture is the 55-gallon (this tank is only about 3 months old, however I have used this same setup on many tanks) second picture is the 75-gallon setup.

View attachment 1046250 View attachment 1046252

Beautiful tank! What are you using for outlets? You can't even see them!

I am unfortunately fairly limited on the filter choices. Eheim and Fluval are sparsely available and come with ridiculous price tags because of it. ADA and Oase are nowhere to be found, so the "premium" filter of choice here is Atman. It certainly is not a bad filter but it does lack some of the features such as pre-filters. The 3337s line that'll use does 1,500 lph so a combined 3,000 lph. Which would be a perfect 10 times turnover and 25 liters of "bucket volume".

Do you think your 75g would be running as well as it is now with just 1 co2 system? Have you ever had any problems with flow or build up areas?

 

[TheNewEra]

I just used the basic inlet and outlet pipes the filter came with. I like the lily pipes; however, my tank is kind of built into my desk area so it would be hard to get a glass lily pipe off to clean it periodically. Yes, one CO2 setup for a 75 gallon is plenty, I just did two because I could go longer without having to replace the tank. If I removed the second one I would just increase the CO2 flow on the first one to make up the difference.

The factory outlet is more like a spraybar though right? Don't you get different flow patterns with those? I hear you on the cleaning though, those lily pipes brushes do require the pipes to come off first even then they can get stuck at times..

Is that 1500 LPH out of the box? Either way one filter should be more than enough to generate enough flow for co2 and dissolved ferts. You really don't need two filters as most of the filtration will eventually take place in the tank between the plants and surfaces mostly the substrate.

It sounds like you have nice aesthetics, why do you want to put more equipment in it. Just run the intake back left or right and the return on the same side but toward the front, so you get flow growing across the front and around the back.

1 filter would probably be enough but I am a big fan of redundancy, plus it also depends on the scape right? An open scape like @woody123 has above could get flow with 1 filter, but with a very densely planted "islands" design with 2 incredibly dense back corners or very hardscape heavy scape I would be stressing if the backflow will manage to push the flow back through the back. Having the additional filter then would be great.

Filtration is not really a big concern for me to be honest, like you said, the substrate and plants will do good job taking the no3 out of the tank. Beyond that, I always just fill up 2 out of 3 media buckets in the filter with matrix leaving 1 for mechanical filtration. This also also one of the reasons why I want 2 filters, 1,500 lph out of the box is great, but it is still a manufacturing statement. It could be lower, or higher, in practice. 1,500 lph is also based on the default filter media, so as soon as I fill up it properly with media the flow will get hampered a bit right? Then we still have the oversized reactor, which, if I recall correctly can slow down flow up to 10%

I found this video from Green Aqua that does go into this subject, I love Green Aqua but I rarely take anyone's advice at face value, especially not on YouTube. Close to the end they talk about conflicting flow to create full circulation. In short, a hardscape heavy design could benefit from having 2 outflows pointed directly at each other. Meeting up in the middle and the opposing flow would then force the water to the back of the tank and so making a separate circulation in each half of the tank. In theory this also sounds this makes sense, but has anyone had any experience with this? Theoretics in aquascaping more often than not do not work in practice.

Planted Tank EQUIPMENT Placement Guide | How To Install Your AQUARIUM GEAR

Yeah as long as water is moving throughout all areas of the tank, so is your CO2. With 2 filters/intakes/output you can play around and see what works best for you. The only "wrong answer" is a setup that has dead spots where you don't have any flow. You might even have too much flow running both of those filters lol. You'll figure it out once you get up and running, definitely wouldn't stress it now

Unfortunately stressing and overthinking is in my nature.. In my previous tenure of aquascaping I also ran into a lot of small issues, which makes sense, since it is an ever evolving hobby and a lot of things to learn. Majority of mistakes also came with usual beginner choices of equipment. This is the reason I am troubleshooting the things I am fully sure about, this is the biggest tank I have worked with and it is the first thing people see when people come into the house. So I really want to avoid any mistakes. The first thing people should see when coming in the house is a beautiful scape not a scape that has uneven growth or an algae ridden scape.

I really just want redundancy in the tank, and I keep reading that 10 times overturn should be a good goal to help keep a clean tank. Livestock will be adjusted for flow heavy fish of course, though the majority will be cleaners anyway.

 

[TheNewEra]

Yes, your right out of the box 1500 lph is not real world, probably 1/2 of that. The idea of 10x turnover though is to me fiction. There is no magic number for turnover. This number was out there when people only kept FO (fish only) tanks with big waste makers. This isn't usually the case with planted. The fish are smaller and you have the plants utilizing the waste. If one believes once the tank matures that most of the filtration is in the tank then what is so important about turnover? Aren't we really talking about flow? Lots of people say that about the type of scape, if it's heavily planted you need more. How would plant leaves stop dissolved ferts and co2?

I can actually make a case that it's better for waste to accumulate (other than if it's aesthetically off-putting) in the tank, because your probably removing it once a week with water changes. When it goes into the filter it's still part of the system.

Not saying there's a problem with large turnover, just isn't necessary. I've run many 4-foot tanks with 1x-2x turnover that were completely pristine and they were different types of scapes some heavily plant some mostly hardscape.

Wow, I expected it to be lower, but only half of is given frim the manufacturer? I agree with you on 10 times overturn not being a magic number. Though I do think the advice is mostly aimed at novices and intermediates that maybe don't have a full grasp the skills needed. I didn't know 10x was for FO tanks, I thought the logic actually came about for planted tanks. I've seen the effects of waves crashing into mangroves, the flow of water becomes drastically hampered or even becomes still water. I think the idea of man made mangroves was floated around to prevent tsunamis from getting to dry land. I always figured that's why planted tanks had higher flow, to make sure it pushes through even the most densely planted/built areas of a tank. Giving these "arguments" purely to learn and exchange info not to start a discussion.

Accumulating waste being a pro due to the added nitrogen? I will definitely do 50% water change every week with extensive vacuuming should the soil be too dirty.

I can understand you managing the same or bigger sized tanks successfully, even on 3times turnover, you definitely seem to have the knowledge and skill for it. I would like to get there as well, but for now I would basically do anything to limit to chance of algae.

1 more thing that I forgot to add at the start, I live in a tropical environment so temps are fairly high. For this reason I will be running fans on the tank, but I did not actually stand still that blasting a fan into the water could change the flow pattern I set up. How much does a fan actually influence flow patterns?