10,000 gallon "moat" in a geodesic dome

Dragonstar · Mar 17, 2021

For many reasons I've decided to build a 38' diameter geodesic dome to house an aquaponics system. This will be the culmination of many years of ideas and components coming together. I'd like it to be a functional space to grow fish and produce to eat, and also an idyllic retreat for relaxing, like those butterfly gardens they have in museums sometimes.

I also want it to be the largest aquarium I have ever known.

I spent hours as a kid in marine aquariums watching the sharks in the huge tanks, and more hours as an adult watching my own tanks. I love museum displays and underwater restaurants and all of the theatrical aspects of good set design. So I'd like my own smaller version of this. Not just for the wow factor and the relaxation, but also because it will help me assess the health of the fish in the tank. Below is a rough idea of what I have in mind:

The dome itself is coming along well. I've also made a 15,000 gal doughnut shaped tank in the ground before. I'm versed in earthbag building, and I've obtained a 10 foot x 3 foot x 3/8 inch slab of acrylic. Now the time has come to figure out if I can actually pull this off.

As you can see above the idea is to have a liner that completely covers the tank interior. I could do that with a 40' x 40' unbroken membrane that drapes all over everything and is tucked down inside the tank itself. This is the pond approach, which typically uses EDPM rubber liners. Another option is to use laminated polyethylene geographical textiles used to make soil retaining walls, such as 24 mil UV stabilized Dura-Skrim. (https://www.buildsite.com/pdf/ravenindustries/DURA-SKRIM-R24BV-Product-Data-1433858.pdf)

The reason I'm posting here is because I'm looking for ideas of how to create a waterproof seal between liner and window. Silicone sealant adheres well to LDPE, but poorly to acrylic. Weld-on works for acrylic but poorly for LDPE. I don't even know how I'd bond EPDM to acrylic. I used to refer to a chart that describes how to glue one surface to another but I can't find it anymore.

I could create a frame , carefully drill holes in the acrylic, and bolt the liner between the window and frame with some sort of gasket.

The good news is I can create the bond in advance on a table using clamps before installing it, then fill in the tank. The slab I have is flat. For aesthetics I plan to heat bend it into a curve but if it serves the project I don't have to.

If you have an idea of how I could pull this off I appreciate it!

WIReefer · Mar 17, 2021

That sounds like it’s going to be amazing. I don’t have any experience with this but I’m definitely going to be following!

Breadman03 · Mar 17, 2021

I think I read that silicone on large panels is really just acting as a gasket and not a structural support. Water pressure keeps the panel pressed against a mounting flange with that silicone gasket in between.
Check out Bill Wann's tank. He's posted tons of info about it and you might find some of your solutions there.

CMMorgan · Mar 17, 2021

I have designed kitchens, baths and bars in geodesic domes but never an aquarium. Gobsmacked - this is awesome. Can't wait to learn more.... where will the filtration be? Will you be viewing this from above also or just the "little" 10' window? Are you in Florida? LOL Hoping there will be an open house --- #road trip!!
To answer your question... what about a transition from liner to fiberglass to acrylic viewing panel? There are more than a few acrylic monster builds out there that can offer advice. Also, we have a couple reefers that work in the professional setting that may be able to jump in here.
Following for sure! Who doesn't like donuts?

JMetaxas · Mar 17, 2021

Following !

dedragon · Mar 17, 2021

very cool, but what plants were you thinking of growing with marine fish tank?

TheDragonsReef · Mar 17, 2021

This is really cool, cant wait to see the finished product

Daniel@R2R · Mar 17, 2021

Interesting project for sure!

KomsCorals · Mar 17, 2021

Awesome idea, following along!

davidcalgary29 · Mar 17, 2021

How about creating a large saltwater pool bisected by a submerged transparent tunnel? I recall seeing some hotel and restaurant in the Maldives that had that type of underwater corridor.

alain Bouchard · Mar 18, 2021

Dragonstar said:
For many reasons I've decided to build a 38' diameter geodesic dome to house an aquaponics system. This will be the culmination of many years of ideas and components coming together. I'd like it to be a functional space to grow fish and produce to eat, and also an idyllic retreat for relaxing, like those butterfly gardens they have in museums sometimes.

I also want it to be the largest aquarium I have ever known.

I spent hours as a kid in marine aquariums watching the sharks in the huge tanks, and more hours as an adult watching my own tanks. I love museum displays and underwater restaurants and all of the theatrical aspects of good set design. So I'd like my own smaller version of this. Not just for the wow factor and the relaxation, but also because it will help me assess the health of the fish in the tank. Below is a rough idea of what I have in mind:

The dome itself is coming along well. I've also made a 15,000 gal doughnut shaped tank in the ground before. I'm versed in earthbag building, and I've obtained a 10 foot x 3 foot x 3/8 inch slab of acrylic. Now the time has come to figure out if I can actually pull this off.

As you can see above the idea is to have a liner that completely covers the tank interior. I could do that with a 40' x 40' unbroken membrane that drapes all over everything and is tucked down inside the tank itself. This is the pond approach, which typically uses EDPM rubber liners. Another option is to use laminated polyethylene geographical textiles used to make soil retaining walls, such as 24 mil UV stabilized Dura-Skrim. (https://www.buildsite.com/pdf/ravenindustries/DURA-SKRIM-R24BV-Product-Data-1433858.pdf)

The reason I'm posting here is because I'm looking for ideas of how to create a waterproof seal between liner and window. Silicone sealant adheres well to LDPE, but poorly to acrylic. Weld-on works for acrylic but poorly for LDPE. I don't even know how I'd bond EPDM to acrylic. I used to refer to a chart that describes how to glue one surface to another but I can't find it anymore.

I could create a frame , carefully drill holes in the acrylic, and bolt the liner between the window and frame with some sort of gasket.

The good news is I can create the bond in advance on a table using clamps before installing it, then fill in the tank. The slab I have is flat. For aesthetics I plan to heat bend it into a curve but if it serves the project I don't have to.

If you have an idea of how I could pull this off I appreciate it!

@AlexG made a tank with pond liner where he tested different bonding; I think he was using acrylics window. maybe he can help you

Dragonstar · Mar 18, 2021

Thanks for the leads, I will definitely look into those and see what might work.

This will be a freshwater 10,000 gallon doughnut inside of a greenhouse. The filtration will be aquaponics via the principles of Waste Transformation Farming. As we all know, one of the big downsides to keeping fish is having to process the waste they produce. Two of the pain points in raising vegetables is you have to fertilize them, and also water them. Well, aquaponics neatly solves both problems in a reciprocal fashion. The fish excrete waste, which the plants love. The plants filter out the waste, which the fish love. If you add vermiculture into the mix, the worms aerate the plant roots and also feed the fish supplemental protein. Win Win Win.

The plants I'm planning to use for filtration are mostly above-surface greens. Lettuce, kale, beans, peas, tomatoes, squashes, melons, that sort of thing. I will have more exotic plans around too, such as mangoes, pineapples, dragonfruit, bananas, citrus trees. But those probably won't be used for filtration.

I specifically want a doughnut shape because I want to introduce a current. Ordinary aquaponics tanks are static. They have some movement but the fish just laze about aimlessly. There are also channel farms with long tanks that sortof have a current, but it inevitably comes up against a back wall. It definitely works, but because of long real estate which I don't have. I want a combination of pump intakes, return outlets, and powerheads to produce a continuous flow so the trout are constantly swimming in current, as they do in nature. This helps with their health via reduced stress and also adds on muscle. Trout in particular are designed to exist in flow. They are more efficient and happy that way.

The fish I'm considering are:
Tilapia (are OK in static waters or in a current)
Bluegill (probably would rather be in more pond-like waters but we'll see)
Rainbow Trout
Channel Catfish (down for whatever)
Feeder Minnows

Dragonstar · Mar 18, 2021

CMMorgan said:
I have designed kitchens, baths and bars in geodesic domes but never an aquarium. Gobsmacked - this is awesome. Can't wait to learn more.... where will the filtration be? Will you be viewing this from above also or just the "little" 10' window? Are you in Florida? LOL Hoping there will be an open house --- #road trip!!
To answer your question... what about a transition from liner to fiberglass to acrylic viewing panel? There are more than a few acrylic monster builds out there that can offer advice. Also, we have a couple reefers that work in the professional setting that may be able to jump in here.

I mean, a bar would not go awry here.

The surface of the water will be at foot level just as in a typical koi ponds with bridges and such. But the center "island" will be more like a well with stairs down into it. That's how the window will work, it will be like a cutout in the retaining wall. So the central 16 feet of the dome will be recessed 3 feet down into the ground.

Fiberglass is a good idea. Really, I'll take any idea at all, I am completely unlimited at this point as long as all surfaces are food-safe.

piranhaman00 · Mar 18, 2021

How about some flathead cats? One of my favorite fish!

Dragonstar · Mar 18, 2021

piranhaman00 said:
How about some flathead cats? One of my favorite fish!

Done!

Waydeo · Mar 18, 2021

I vote for catfish . That's your meat and add some fresh veggies grown from the waste byproducts. All you need is to do some homemade beer and open a resturant right there.
Call it " From tank to table " lol

N.Sreefer · Mar 18, 2021

Im really excited to see this, great idea. Im a horticulturist if you have any questions about the plants. One piece of advice pineapples are bromeliads they wont do well in aquaponics.