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Setting up a new 300 gallon tank need some advice


AC Members
Hello new member here, I've been doing saltwater fish for a couple of years now with a 75 gallon tank. I recently purchased a 300 gallon tank and i'm working on setting it up, I need some advice here.

My tank is 10ft long and has 2 Built in overflows, I have an old 55 gallon aquarium that can fit underneath my stand, I was thinking of using it as a sump. With my 75 gallon tank I've only used a cannister filter and hob skimmer just a basic setup.

My main question is what I need to setup this 55 gallon as a sump underneath with my heaters and a skimmer underneath it. I know I will need a pump but do I just need 1 pump or will I need 2 to pumps? 1 to pump the water down into the sump and another one to pump water back into the tank? I'm really confused here and how to setup this tank with my overflows, do I fill the tank up to just beneath the overflows or what?

I've included some pics of my tank, like I said I would like to use a 55 gallon tank as a sump underneath with heaters and skimmer in it, I also considered using a fluval X5 Cannister filter on the tank in addition to the sump any thought on that?

I'm also looking at filling it with some sand, I've seen people have used play sand from Home Depot, but diatoms could be bad, but that play sand won't buffer the water like argonite sand will would it? I'm only doing fish with live rock so will that matter too much? Since I have my 75 gallon up and running I was think of just using some water from it and not even have to worry about cycling my tank but how much aquarium water would it take for this to happen going from 75 to 300?

Any help would be appreciate thanks!


IMG_20130528_123337.jpg IMG_20130528_123406.jpg IMG_20130528_124202.jpg


AC Members
You'll need the return pump, the overflows do not require any pump to bring the water down to the sump. You'll also need a few pieces of glass cut to make the seperate chambers. Plus you may want a filter sock mount. Then of course whatever hardware you'll be putting in skimmer, heaters, reactors, etc.

With the sump you wont need any extra filtration from a canister. If you have enough live rock you may not see much of a cycle

I would definently stick with araganite sand, as you said the play sand wont offer any buffering capability and likely to cause diatom blooms.

Water in your 75 will not help with cycling at all, the good bacteria in your 75g would be contained in your sand, live rock, and filtration media.


Josh Holloway--Be mine!!!
I agree with TLsquid. Depending on what you put into the tank, looks like you ready to go.


AC Members
Thanks for the Reply, how would I divide the 55 gallon sump up, is there a certain way I should do it measurement wise? I guess I would need to leave room for my protein skimmer to sit in the sump, but how about the other 2 spots, and can my protein skimmer sit next to the pump or does it need to be in a separate chamber?I like the idea of running carbon, is there a way for me to use carbon with my sump as well.

I'm still not sure about the overflows, I have 2 of them built into the tank, with the holes you see in the picture, I guess one can drain into the sump on one side and the other can pump water in on the other side, is that how i should set it up? I have two holes in each one so I'm just not sure how to set this up with the sump, any ideas you can give me?

While i'm typing this, I guess I would have my pipe inside the overflow getting water shot up from the pump in the sump and it shooting out the little v on the inside of the tank, but I'm still not sure on how I should plum all this in together so help me out if you can lol.


AC Moderators
1st, congrats on the tank!

Can we get a couple more pics of the tank? What are the dimensions? 10'x?x?. Anymore pics of the return nozzle? How is the return secured to the acrylic?

If the acrylic has scratches somewhere you don't want them to be, you may want to consider buffing those out before itis filled.

You only need one pump and should only use one pump unless you go with a closed loop for flow (doubt that will be the case but may want to research it as an option).

Your drains work on gravity. Do not attempt to pump water down, only up. You should google "herbie drain". Each overflow box will contain 2 drains anf you'll bring the return pipe(s) up over the top with 90 degree elbows. This will allow full siphon, quieter overflows with a backup drains for safety. At a minimum google "durso drain". I highly recommend that you hard plumb (glue/pvc) your drains all the way to the sump and at least most of your return plumbing (you're dealing with a good amount of water). Soft tubing should only be connected just at the return pump output to reduce vibration (not required). Use plastic hose clamps to secure the tubing if you use any. If you use an external pump, you'll want to hard plumb everything for the return. External pump may be your best option due to the size of the tank.

Make sure your bulkheads are not cracked or dried out. If so, replace them (again, lots of water).

Don't use play sand, buy aragonite go bare bottom. Seriously, don't use it :)!.

Lots of sump designs out there. Some use refugiums, some just skimmers. With a tank that size you should plan on using at least 1 reactor to run media. The cansister could be used but you'll need to keep it clean (about the only thing you can use a cansister for on this tank). Measure the inside width of the 55 (or google that) and get glass baffles cut and silicone them in where you want them. Let that cure for a couple of days before putting the sump online. The single most important thing to think about with a 55 sump on a 300 is making sure the sump can handle the back siphon once the return pump is off. The height of you returns (locline is what you have) in the display and the sump baffles will help control this.

You're going to need more flow than what your return will provide. Even though this is a FOWLR, the return alone isn't going to cut it. Go big with powerheads (MP-40, MP-60, large Tunze or the infamous jaebo WP-40). Sorry to bring it up here Khemul :)!

Now the fun part, what fish are you looking at?
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AC Moderators
Not to point you to another forum but you should probably check this page out. The guys/gals in that forum run 180+ minimum (many much larger) . A lot of them are reefs so you won't need to go to the extreme that you'll see but it will give you some ideas for setup.



AC Members
It's 10 feet long x 2 feet high x 2 feet wide. The guy gave me some stuff to clean the acrylic glass, haven't tried it yet there are some slight scratches here and there nothing major I'd say I've also heard you could use sand paper and smooth a scratch out on acrylic anyone tried that? The return is not attached to the tank at this moment, he dismantled all the underneath stuff so I could pick it up 3 hours away from where I live and transport it, so that's what i'm kinda lost on how the setup should go, I think he just had it velco stripped on the back of the tank.

I will definitely get the aragonite sand, I'll post some pics of the bulkhead later this evening, and I wanted to ask a couple more questions.

As for fish I haven't given it too much thought yet, my main concern was getting the plumbing correct first, but I was thinking about a school of Anthias fish and some Chromis fish and I would like to add a few tangs possibly, and a goby I love those. What do you think or any other suggestions? In my other tank I have foxface rabbitfish, a Clown, and a Butterfly fish and a Chocolate Starfish that will be moving over.


AC Moderators
Sounds like some good ideas for fish. You obviously have lots of stocking options.

I would use a herbie in both overflows and then run your return lines up and over the rim of the tank. You can use that locline to thread into the last 90 degree elbow that goes into the display on each return line. The bulkheads will hold the drains in place. There is no need for velcro that I can think of.

Here is the original "herbie" thread...



AC Members
I haven't replied in awhile been pretty busy but I've got some money finally and a little time want to get started on my tank.

Greech give me your idea on this or anyone else for that matter.

I've decided to go away from a 55 gallon sump to a 30 gallon (I think) it's easier for me to fit the 30 under the stand, if I were to put the 55 I'll have to slide the tank out and put the 55 in through the side, but I think the 30 will be easier for me to maintain and work in underneath.

I want to keep things simple, so I thought I would just use 1 overflow and have it drain into the sump where my heaters, uv sterilizer, and skimmer will be and I was thinking I would just plug the other drain or overflow. Then I want to just run a Canister Fluval X5 and have it do my filtration. Will that work for me?

Also what kind of external pump would you recommend for my sump?

I had a question about power head use in this tank look at where my opening are, to put powerheads on the side of the tank how can I make that work? the power cord would have to run inside the tank, since there is no space to drop them in on the back wall of the tank?

Just wanted some feedback before I finally make my purchase, like I said there are probably better ways but I just want to keep it real simple for me without doing a lot of plumbing underneath. Thanks for the advice!


AC Members
I've been thinking it over that's probably a dumb idea, my previous post. I think I should use the 55 gallon as a sump and hook it up the way it supposed to be.

Here is a picture of the Bulkhead, it's 1 inch.

And here is a pic of the return line I believe that goes off the spout of the built in overflow I assume cause it fit's there perfectly and does it just run down into the sump just like that?

So with 2 built in overflows I would have 2 drain lines going into the sump with the flex hose above, but then I'm confused what goes through the bulkhead? because my return from my sump will go up over the top of the tank and 90 degree elbow back into the overflow box correct?

Also what pump would you recommend for me to use, internal or external and what rating to give me good turnover, remember I'm doing fish only.

I know I'm making this harder than it is, but I've got to get it right I can afford to do it wrong and waste any money on setting it up wrong.

Thanks again!