Custom 300+ Gallon Tank Build

[FrozenFishSticks]

Hey what’s up everyone, I’m relatively new to the hobby and needed suggestions on a new tank I’m currently planning. I currently have a 10, 20, (2) 30’s, 45, 55 and a 75 gallon already setup. As I was browsing the deep dark web (just kidding) I came across a couple of tanks that were close to my price range. Most of the tanks had the measurements or size included in the post……..except 1. I messaged all the sellers with my offers and surprisingly got answers back from all of them. Since they all answered I had to really put some pressure on the sellers with some annoying but reasonable questions. Ex. How old is the tank? How are the silicone seams? Was it saltwater or freshwater? Does it leak? You get the picture of the types of questions. After getting the answers it was finally the hard part, making the decision. So initially I was looking for anything bigger than the current 75 gallon I have. My goal was a 125 or 150. (I might have tried to lowball a couple people who were selling a 180 or 220 haha no shame here) Okay so one of the listings just kept catching my eyes, I now know why. I’m probably the worst at guessing the size of a tank from a picture with no reference points to gauge the size. This is important because remember when I said one listing didn’t have the tank size and the seller didn’t know it either. I ended up making a lower offer based on the limited knowledge I had at the time. The offer was $200 if I came to pickup the same day. (By the way that is the best way to get people to accept lower than normal offers) The seller immediately accepted the offer, so at that point I was committed to that tank because of the price alone. At this point I’m super excited, I didn’t know the size of the tank but knew it was bigger than my 75 and looked like a 125 or 150 to me. (Amateur) As I was preparing the uhaul rental the seller messaged me and said btw your going to need like 5 guys to move it.……..Pause………I’m not a body builder but I’m also not weak so I’m thinking to myself how could it need that many people to move. He then sent another message saying it’s probably about 600lbs. It was around then I starting to panic, I already told him I could pick it up today but there was no way I could get the help to move that much weight in a couple hours. Knowing that I couldn’t move the tank I then asked the seller if he would be okay if I came to pick it up sometime tomorrow. Long story short he agree and I started calling all my friends for help. Tomorrow came I had the help lined up and was just waiting on the sellers green light. Once I got the green light and got to see the tank in person I was overwhelmed. I measured the tank and it was 72x36x28, that’s 300 Gallons!!! what the heck!! Did I really just find a 300 gallon tank for $200? Got the tank loaded and unloaded at my house. While I was unloading I saw that one side of the tank was super clear, yeah I know I don’t know how I missed it at first. I guess I was too excited haha. After doing some research I found out that it was a manufactured tank, the only manufactured tank of its size. It turned out to be a Marineland 300 DD with the ultra clear viewing glass. At this point I’m literally jumping up and down, I would have bought this tank for $200 if it was cracked lol. Just for the glass alone, the bottom is 3/4 glass and sides are 1/2. Finally getting to the point on why I started this thread. So I now need to build a temporary platform to do a leak test on and a custom stand. For the leak test platform I want to use the least amount of wood possible being that it’s only to test for leaks. For the stand I have a couple ideas on how I want to set it up but don’t know the best route to take. Also do you recommend I fully rebuild the tank? Any help or ideas would be greatly appreciated. If you live near the Virginia area any physical help is appreciated also. I’ll bring everyone along with the build on a build thread when I start the work. Also plan on starting a YouTube channel to document my adventures progressing into this amazing hobby!!

The second picture is the only one that the seller had on listing. And some are from before I cleaned it. Also is it okay for it to be sitting on its front panel?

 

[FrozenFishSticks]

Here is the design I had for the stand. I know how I want it to look just don’t know the strongest possible way to build it. I’ve watched tons of videos but really wanted to know the best design structurally. Also don’t know what would be the best way to give me that refugium viewing panel, I thought about daisy chaining 3 separate tanks (2 smaller sumps 1 refugium) or using 1 bigger tank with dividers. The main problem is idk if the return pump pull force would make it impossible for fish to live there.

The first picture is just an idea I had but also don’t know if it’s possible. Could I have the 300’s overflows running to 2 tanks then have those 2 tanks overflows running to the sump? Therefore allowing me to have 4 tanks filtered by 1 sump system.

 

[cilyjr]

Good find. I spent 2k on mine. 320 gallons.
I did not see an overflow in the pictures. Is it drilled?

 

[FrozenFishSticks]

Good find. I spent 2k on mine. 320 gallons.
I did not see an overflow in the pictures. Is it drilled?

Thank you, I can’t wait to get it up and running. I’m definitely going to be losing sleep with all of this research haha. Yeah it is drilled on both sides, (2) 1 1/2 and (2) 1 inch. Am I missing the weirs or could it have been ran without them?

 

[cilyjr]

Thank you, I can’t wait to get it up and running. I’m definitely going to be losing sleep with all of this research haha. Yeah it is drilled on both sides, (2) 1 1/2 and (2) 1 inch. Am I missing the weirs or could it have been ran without them?

It could have. I'd put some in. I'm pretty sure you can order OEM ones from marineland or you can just build them.
1/4 or 3/8 thick acrylic would do the trick.

What are you gonna do for lights?
I'm using 8 hydra 32hds and 4 t5 lamps.

 

[FrozenFishSticks]

Alright that’s 1 of the questions I had on my list. I figured I’d have to make some but didn’t know what size acrylic yet. For the lights I’m not sure yet, I’m still trying to figure out if im doing saltwater or freshwater. It was setup for saltwater but I have 0 saltwater experience and don’t want to mess up. Would it be hard/expensive to maintain a saltwater tank this size?
@cilyjr

 

[1000rrstunna]

Buy weirs on eBay. Search overflow box.
BE GENTLE WITH THAT TANK the 300dd were notorious for seams bursting.

 

[1000rrstunna]

Btw that was a killer deal if I was you I’d flip it and buy a 180 new when they go on sale.

 

[cilyjr]

Alright that’s 1 of the questions I had on my list. I figured I’d have to make some but didn’t know what size acrylic yet. For the lights I’m not sure yet, I’m still trying to figure out if im doing saltwater or freshwater. It was setup for saltwater but I have 0 saltwater experience and don’t want to mess up. Would it be hard/expensive to maintain a saltwater tank this size?
@cilyjr

I guess expensive is subjective.
I am not really sure what my monthly expenses are.

If you have no equipment, that's gonna cost to get you running. Also what your goals are will depend on your initial cost.

It's not hard. I have automated most of my maintenance chores.

 

[cilyjr]

Btw that was a killer deal if I was you I’d flip it and buy a 180 new when they go on sale.

This is a good idea, especially if you have no equipment to run a 300 gallon tank.

You'll save money on less powerheads, lights, rock, smaller skimmer... You get the picture.

My lights alone cost $4000 retail.

 

[FrozenFishSticks]

Buy weirs on eBay. Search overflow box.
BE GENTLE WITH THAT TANK the 300dd were notorious for seams bursting.

I think I’ve seen that when searching these up. It looks like the inside seal might have been redone. That’s why I was thinking about rebuilding it fully. I know it would be a huge pain to do that but I’m willing to try.

Btw that was a killer deal if I was you I’d flip it and buy a 180 new when they go on sale.

Thanks I was surprised when he accepted my offer. He was a property manager and the business owners who rented before left it and he had to clear out the building. He said other people messaged him for full price the next day haha. I have definitely thought about flipping it in order to help finance getting into saltwater but I’m hesitant because it’s not often you run into a tank this big for the price.

I guess expensive is subjective.
I am not really sure what my monthly expenses are.

If you have no equipment, that's gonna cost to get you running. Also what your goals are will depend on your initial cost.

It's not hard. I have automated most of my maintenance chores.

Yeah I realized after I posted the question “expensive” for some might not be for others haha. To better reword the question, what is the most expensive part of maintaining a saltwater tank? How much would the water changes cost per month for 300 gallons? How much RODI replacements? I know it won’t be exact but a general ballpark works.

 

[FrozenFishSticks]

This is a good idea, especially if you have no equipment to run a 300 gallon tank.

You'll save money on less powerheads, lights, rock, smaller skimmer... You get the picture.

My lights alone cost $4000 retail.

Would a Fowlr setup cost as much? And are the lights needed only for frags?

 

[cilyjr]

Would a Fowlr setup cost as much? Or are the lights needed for frags?

You only need enough light to see the fish for this.

 

[cilyjr]

I think I’ve seen that when searching these up. It looks like the inside seal might have been redone. That’s why I was thinking about rebuilding it fully. I know it would be a huge pain to do that but I’m willing to try.

Thanks I was surprised when he accepted my offer. He was a property manager and the business owners who rented before left it and he had to clear out the building. He said other people messaged him for full price the next day haha. I have definitely thought about flipping it in order to help finance getting into saltwater but I’m hesitant because it’s not often you run into a tank this big for the price.

Yeah I realized after I posted the question “expensive” for some might not be for others haha. To better reword the question, what is the most expensive part of maintaining a saltwater tank? How much would the water changes cost per month for 300 gallons? How much RODI replacements? I know it won’t be exact but a general ballpark works.

If you have hard coral you will also need to think about calcium, alk, supplementation.

All of what I'm gonna say below are what I spend and does not necessarily reflect what you would spend.

I buy a bucket of salt every 6ish weeks. 65 bucks for reef crystals.
I figure I spend roughly $100 a month in electricity.
I live on the California coast so my water costs roughly 1 arm and 1 leg a month... I spend roughly another $100 monthly on just the tank I bought a 2:1 RODI unit.

I run a calcium reactor and a kalkwasser reactor for calcium and alk. So I have no idea what 2 part would cost monthly.

 

[FrozenFishSticks]

You only need enough light to see the fish for this.

If I did saltwater I’d probably start there and progress towards reefs.

If you have hard coral you will also need to think about calcium, alk, supplementation.

All of what I'm gonna say below are what I spend and does not necessarily reflect what you would spend.

I buy a bucket of salt every 6ish weeks. 65 bucks for reef crystals.
I figure I spend roughly $100 a month in electricity.
I live on the California coast so my water costs roughly 1 arm and 1 leg a month... I spend roughly another $100 monthly on just the tank I bought a 2:1 RODI unit.

I run a calcium reactor and a kalkwasser reactor for calcium and alk. So I have no idea what 2 part would cost monthly.

I definitely want to do coral but most likely later down the road. Thank you for those #’s, I can get a rough estimate from those. What kind of heating are you running? Im leaning towards the water heater method but still a little confused about the setup. Btw I saw your whole setup, it is beautiful!! Definitely goals!! The tank came with some live rocks, a 2 sump setup, half bucket of salt and jebao 6500 return pump. What else would I need for a basic setup? Is the protein skimmer needed? And how long can RODI water be stored?

 

[cilyjr]

If I did saltwater I’d probably start there and progress towards reefs.

I definitely want to do coral but most likely later down the road. Thank you for those #’s, I can get a rough estimate from those. What kind of heating are you running? Im leaning towards the water heater method but still a little confused about the setup. Btw I saw your whole setup, it is beautiful!! Definitely goals!! The tank came with some live rocks, a 2 sump setup, half bucket of salt and jebao 6500 return pump. What else would I need for a basic setup? Is the protein skimmer needed? And how long can RODI water be stored?

Buy used stuff. Look here in the for sale forum.

As far as protein skimmers, some say no. I think yes.

RODI, Indefinitely. I have a 32 gallon reservoir that supplies my top off and kalkwasser reactor.

 

[FrozenFishSticks]

Buy used stuff. Look here in the for sale forum.

As far as protein skimmers, some say no. I think yes.

RODI, Indefinitely. I have a 32 gallon reservoir that supplies my top off and kalkwasser reactor.

Alright I’ll look into a protein skimmer and good RODI unit. I have a new 55 Gallon drum that I was thinking about using for storage. Is there any size recommendations for the skimmer? It would be over 500 gallons for the full system. (Tanks + Sump)

 

[cilyjr]

Alright I’ll look into a protein skimmer and good RODI unit. I have a new 55 Gallon drum that I was thinking about using for storage. Is there any size recommendations for the skimmer? It would be over 500 gallons for the full system. (Tanks + Sump)

Look and see what is available used both here and locally. That's what I'd do when working with a limited budget.

 

[FrozenFishSticks]

Look and see what is available used both here and locally. That's what I'd do when working with a limited budget.

Yeah that’s what I have been doing, I’m thinking I’m probably going to buy someone’s full setup and convert it over to the 300 when it’s up. That way I can get all of the Neptune Controller components, dosing pumps, skimmer (would most likely be too small but I could sell), maybe lights and RODI system all together. I’ve seen a couple good deals but I’m going to wait it out some while I design the leak test platform and stand.

 

[FrozenFishSticks]

@cilyjr How much do you think the tank would sell for as is? It has one broken support that someone replaced with a glass support. Would it be worth it to take off the top trim/brace and euro brace it?