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Discussion Starter · #1 ·
I'm still in the design phase of my 450 gallon tank and one issue is finding a reactor large enough for a 400+ gallon tank. I figure i could split the outflow from the reactor into the 4 returns from the sump or something like that maybe maybe not - but the first part is find the reactor.
 

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Where do people learn how to build a reactor and to properly size it ?
I can only speak for myself, but it was mostly trial and error. There are good resources on here and people that would be happy to help (myself included). There are a couple of main designs that people build (Rex Griggs and Cerges) and neither is too difficult in terms of DIY skills required.

If you want to go down that road and want input, i'm happy to chime in with my thoughts.
 

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Discussion Starter · #5 ·
Sure - it would be good to hear how to do it - perhaps there should even be a sticky design page somewhere - but yea. The tank will have a sump with 4 returns and 4 down flows.
 

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Given the size of the tank your only option is a rex giggs style reactor. Its just a tube with water flowing from top to bottom and co2 being injected into the side near the top. The water flowing downward breaks up the bubbles into micro bubbles and then absorbs them. The longer the tube and the faster the flow the more co2 you can dissolve for a bigger tank. Most people have a tube around 24" long or less for 120 gallon tanks and smaller. I would guess you would want at least 3 feet of tubing. This is taller then most stands. Other options include using a smaller reactors and just not getting a 30ppm dissolution of co2, even small amounts of co2 are helpful.
 

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Can't size it up because they are limited to the size of those filter casings, unless you plan to just run less.
But you can get the commercial housings in pretty damn big sizes. I would be surprised if a 20" housing that takes the big 4.5" cartridges (size 4 below) couldn't get a decent pH drop in a tank this size on its own. Even if it couldn't, chaining two together almost certainly would.

1031464
 

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But you can get the commercial housings in pretty damn big sizes. I would be surprised if a 20" housing that takes the big 4.5" cartridges (size 4 below) couldn't get a decent pH drop in a tank this size on its own. Even if it couldn't, chaining two together almost certainly would.

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Didn't consider chaining them together. So that way is probably a solution for a tank this big. Not sure about the size 4 by itself. 450 gallons is a lot of water. It all depends on how fast you can run water through one of these things and still get good dissolution and I at least don't have numbers for that. Rex giggs though is just a matter of increasing the length of the tube, you could dissolve all the co2 in the world in a rex giggs with a big enough tube and enough water.
 

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Didn't consider chaining them together. So that way is probably a solution for a tank this big. Not sure about the size 4 by itself. 450 gallons is a lot of water. It all depends on how fast you can run water through one of these things and still get good dissolution and I at least don't have numbers for that. Rex giggs though is just a matter of increasing the length of the tube, you could dissolve all the co2 in the world in a rex giggs with a big enough tube and enough water.
I haven't ever tried to get co2 into a tank this big, so I am speculating... though I think the guy with the 300g journal used a single Cerges. Not sure what kind of drop he's getting.

I guess it depends on whether or not you have basement filtration or if it's all going under the stand. With under-tank filtration I think chained cerges may be the best bet.
 

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I haven't ever tried to get co2 into a tank this big, so I am speculating... though I think the guy with the 300g journal used a single Cerges. Not sure what kind of drop he's getting.

I guess it depends on whether or not you have basement filtration or if it's all going under the stand. With under-tank filtration I think chained cerges may be the best bet.
Was actually just re-reading that journal last night. If I remember correctly he had a drip around 0.8 but I dont think he mentioned ever having issues with gas build up. Granted, it was in the basement so it had a significant amount of back pressure so I'm sure that helped.

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Discussion Starter · #15 ·
So, OP - where are you going to have your sump? Does your reactor need to fit in your stand?
The plans might change because it is a bit complex but the current plan is to put the sump in the basement the room adjacent to directly below the tank (the area directly below is unfinished crawl space). So to put the sump in the basement the pipe will have to run a bit horizontal to get to the room next to the area directly below the tank - if we go that route (the alternative would be to put the sump in the stand directly below the tank) the horizontal distance would be approx 22 feet which is a bit of pvc and would require a bit of upsizing of the pumps x 4 to move the water that distance. The vertical distance would be approx 13 feet.
 

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That is the current plan but i suppose one large pump might work with 4 returns - so plans might change. I think i should have a min of two pumps just for fault tolerance.
It seems like the choice of which and how many pumps will come down to noise tolerance. Is there living space in the basement where the sump might go? If not, and if you can put the sump down there, you could use something like an Iwaki that's bulletproof but loud. If you have to move a bunch of water (say, 7X turnover at 3,150GPH) with an under-stand sump, multiple (maybe just two) pumps might be better. You could run two DC pumps at low[ish] power to keep things quiet (something like a pair of Red Dragons, for example). In any case, the number and location of pumps will in part dictate your reactor options.

Let's say your sump is upstairs and you have two pumps, each feeding two returns. In that case, you could have a single Cerges (size 4 housing) on each one. No need to chain them. In fact, as long as you have multiple pumps, I think you're better off with multiple reactors too. Even if you can make a single reactor big enough, it would be better to have the co2 infused water entering the tank at multiple points.

If you're in the basement with a single, bigass pump, you could make a really tall Rex Griggs or a chained pair of Cerges reactors. I'm not sure how comfortable you are with DIY stuff like cutting and cementing PVC... Cerges can definitely be less intimidating if that's not your bag. For example, here's a reactor I made for a small tank. It's got a bypass (you'll need that to control the flow through your reactor) and was assembled entirely with threaded fittings:
Power tool Automotive tire Window Engineering Gas


This sounds like a really big, and really fun project. I hope you start a journal once you get it off the ground!
 

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Discussion Starter · #19 · (Edited)
In post #15 i said i intend to put it in the basement below the tank but it is a bit convoluted since the piping has run a bit horizontal to reach a finished (environmental control) room.

It seems like the choice of which and how many pumps will come down to noise tolerance. Is there living space in the basement where the sump might go? If not, and if you can put the sump down there, you could use something like an Iwaki that's bulletproof but loud. If you have to move a bunch of water (say, 7X turnover at 3,150GPH) with an under-stand sump, multiple (maybe just two) pumps might be better. You could run two DC pumps at low[ish] power to keep things quiet (something like a pair of Red Dragons, for example). In any case, the number and location of pumps will in part dictate your reactor options.

Let's say your sump is upstairs and you have two pumps, each feeding two returns. In that case, you could have a single Cerges (size 4 housing) on each one. No need to chain them. In fact, as long as you have multiple pumps, I think you're better off with multiple reactors too. Even if you can make a single reactor big enough, it would be better to have the co2 infused water entering the tank at multiple points.

If you're in the basement with a single, bigass pump, you could make a really tall Rex Griggs or a chained pair of Cerges reactors. I'm not sure how comfortable you are with DIY stuff like cutting and cementing PVC... Cerges can definitely be less intimidating if that's not your bag. For example, here's a reactor I made for a small tank. It's got a bypass (you'll need that to control the flow through your reactor) and was assembled entirely with threaded fittings:
View attachment 1031499

This sounds like a really big, and really fun project. I hope you start a journal once you get it off the ground!
 

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As your formulating your water moving plans you might want to take a look at pond pumps. I've been shopping for pond equipment lately and was see that a lot of folks us pond pumps on larger tanks. I've got a Sequence brand self primer on my pond that has been running 24/7 for about 20 years now.
 
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