Pratyahara Tanks is the worlds first completely open source tank manufacturer. Our tank is constructed from 100% off-the-shelf parts. All construction details (tank plans) are publicly available.

To build a pratyahara tank is simple.

MATERIALS

1. 2 360 gallon containment tanks – one will hold the water, one will serve as the top of your tank
2. A large number of parts listed in my amazon store. I also recommend Doctors Foster and Smith because of their excellent return policies, technical expertise, and low prices on next-day Saturday delivery.
3. 7 pieces of plywood
4. 2-inch thick styrofoam
5. 2 inflexible rods – used to prop up the tank top while adding salt. pvc or hard wood dowels 4 1/2 feet long are good – picture … this is during your build phase. Ultimately you want to attach drawer guides (glides) between the bottom and top tank so you can slide it top as shown in this picture
6. a hydrometer to measure salinity of the water. I suggest the VWR Precision Specific Gravity Hydrometer with specific gravity range 1.240 to 1.310

STEP-BY-STEP-INSTRUCTIONS

1. The base of your tank is a tarp, some 2x4s and 2 inch thick styrofoam – picture
2. Then you put down one containment tank
3. Then place the 2 aquarium heaters in the back of the tank (towards the part where you plan for your feet to be). I would suggest that all electrical outlets be protected against ground fault.
4. Then place the pondmaster pump/filter just in front of those heaters
5. Put the 2nd containment tank on top of the first – picture
6. Drill holes in both tanks and slide a cinch through the holes to make your hinged door – picture , picture 2
7. Fill the tank: start with just a few inches of water, enough to cover the heaters. Let that get up to 94 deg F, making use of an external thermometer as reference point. Then add more and more water. But never more than 250 gallons total. See the calculations for how to convert inches of water into total gallons as a function of the tank dimensions.
8. Salt the water. Slowly. 1 bag at a time, with advice from ask floattalk to help you.
9. Unplug all electricity and float

CONCEPTUAL TANK DISCUSSION

The Tank Room

A nice tank room that can be comfortably heated is wonderful. Here are other things to consider about the room itself.

electricity

Here is a formula:

watts / volts = amps

since most houses are 120 volts and 15 amps, this implies that you can pull at most 1800 watts of power. So buying 2 1000 watt aquarium heaters is not going to work with standard setups: I know, I threw my fuse breaker when I tried. I have 1 1k watt and another at 300 watts and so far that is fine.

You could re-wire the power from the breaker to the power supply with a different guage wire, or get dedicated wiring, but the purpose of this project is to make everything work with off-the-shelf standard parts and settings.

dimensions

3 feet longer and wider than the tank seems to be an absolute minimum

restroom

A restroom near/attached to the tank room is very convenient.

Tank

Get two 360 gallon containment tanks from NTOTankOutlet.

Tank Framework

Lay down a tarp

You need to get the tank off the floor with some 2x4s. And then put 2-inch styrofoam over that. A floattalk thread discusses this in detail.

Next, simply put the two containment tanks on top of each other like this:

Then drill holes in one side and cinch the top to the bottom on one side to create a hinge like this:

I actually think padlocks are better than plastic cinches because you will find yourself taking them off and on to situate the heaters and also when you drain the tank for cleaning you will need to take off the top. Finally, some people are claustrophobic and would prefer to float without a top.

Spa Pack (pump/filter)

In order to filter the water and warm it, you could get an electronic spa pack from a place like SpaGuts.com but you will need dedicated wiring for that.  Instead, we have to go with a sealess mag drive pump and filter modules.

I’ve found 2 good choices (LifeGard Aquatics and Pondmaster) and I went with pondmaster

Pondmaster

Here’s the data sheet and here’s your link to Foster’s and Smith. And where would we be without me trying to get a commission with an amazon link:

LifeGard Aquatics

• we want a sealless magdrive pump that can deal with 350 gallons of saltwater (though we will only have 250)
• we a triple capacity mechanical filter for particle filtering
• we want a triple capacity chemical filter that has carbon in it
• ultraviolet filtering is loved by some professionals. others think it is a waste of time
• ozone in a closed space will kill a lot, but might also kill you. So let’s drop that also.
• hydrogen peroxide will become a good friend of ours
• weekly and monthly sanitization tips are forthcoming

Temperature Control & Monitoring

Water Thermometer

Submersible Aquarium Heater

In between floats, you need to keep the water warm or the epsom salt will precipitate. So you need a good aquarium heater for that. While 300W is just fine for 300 gallons when you speak of waterbed heaters, my experience is that it is not enough when dealing with aquarium heaters. You need 3-6 watts for every gallon of water you want to heat above 80 deg F. Let’s use 6 watts since we have salt water, whose specific heat capacity is lower than plain water. But on the other hand, you can only have about 1800 watts of total heating at the max. I suggest 1300 to 1600 watts of total heating power. So you’re going to need two 800 watt heaters, one 800 and one 500 or one 1000 and and 300/500 or some combination like that.

Now, there are 7.5 gallons of water in a cubic foot. And so we have the various gallons of water that we can deal with based on total wattage:

• 1300 watts => 216 gallons of water
• 1500 watts => 250 gallons
• 1600 watts => 266 gallons

Epsom Salt

Crop Production Services (sometimes aka Agricultural Garden Supply) is a good place for salt. Look for a place that sells lawn fertilizers. And be sure to check floattalk.

Then setup your spa pack for intake and discharge by adding some piping.

Then heat the water to 104F (the maximum the spa pack is legally allowed to do) and gradually add salt.

Testing for Salinity

You can get fancy and buy a salinity pen, but you can also get the job done for just 10 bucks with these two products:

Filling the tank

First, start with about 3 inches of water. NO SALT. Then submerge your two heaters. Make sure you can get that up to 95 degrees.

Your maximum height is based on how many gallons of water you can heat. Let’s say you can heat 1500 gallons of water. Since there are 7.5 gallons of water in a cubic foot, we can use unit cancellation mathematics to see who many cubic feet of water we can heat:

(1 ft^3 / 7.5 gal) x 250 gal = 33 ft^3

Now the tank we have it quite wide, so the water will not be very high. Let’s convert cubic feet to inches and see how many cubic inches we can afford to heat. 33 cubic feet is 57,024 cubic inches. Now the tank slopes, but the given width and length are 93″ and 69″. So let’s multiply those together and divide that product by 57,024 to get the height available to us. The result is 8.8 inches. Most people recommend 10 inches, but I think we can get by.

Let’s do the 1300 watt calcs

216 gallons is covered by 28.8 ft^3

1 ft^3 = (12 inches)^3 = 1728 inches cubed

therefore 28.8 ft^3 is 49766 inches

So we have 7.75 inches of water available at 1300 watts. That’s not very high. I’ve done it, but dont recommend it.

General Comments

Vendors

Foster and Smith Aquatics has an excellent return policy and incredible rates for next-day delivery on Saturday (and boy do they deliver!). When you are experimenting, you want a company that doesnt make bones with you when returning/exchanging/returning things.

Total cost

• two containment tanks: 655 + 190 S&H = 850
• spa pack with mechanical filter, no ozone: 400 + 50 S&H = 450
• submersible aquarium heaters – 360 + 9  S&H = 370
• water thermometer – 8.00 + 7 S&H = 15

The total cost is 1700.00. Most tanks will run you 2000-3500 used. Then we can add in epsom salt for 300 bucks for a clean 2 grand for the whole deal!

Optional Products

You might want a shockbuster, although you will probably opt to float with all heater power off:

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