Use a pre-owned hot tub?

[Converse]

  I have long been considering trying to get a decent looking hot tub for a fish tank for future expansion.  I could have gotten one today if I had flaggged down a truck that was entering the local "dump".  The hot tub in the back of the pick-up had a VERY nice wooden outside and a nice looking insulated cover.  I could not see inside the tub, but I would have felt it was a good deal if would just even hold water.  Unfortunately (or fortunately) I could not get turned around on the road before the truck  entered the ' dump' and crosssed the scales.  I figured the guy operating the Dump scales would have something to say about taking stuff from the dump rather than leaving stuff there...

 

  So before I go putting ads up in the local area telling the world I'd gladly give a second hand hot tub a good home, I guess I should ask here what are the pros and cons of having a hot tub for a fish tank. Any input ? There are lots of them available on Craigslist listed as "Free".  It is just that this particular one LOOKED very nice, and it was going right past me.... 

 

  So does this qualify for the "you know you are adicted to aquaponics when you want to pull a u-turn to follow a truck to the dump to save a hot tub in the back, and give it a good home?"

 

Sincerely,

Converse

[TCLynx]

I've heard of many systems built from old tubs and hot tubs.  Just want to avoid any metal contact with fish water is the only real thing I would check for.

[Kobus Jooste]

Definately one for the addicted side Converse.  I have recycled pool filter components for my greenhouse before, and have seriously considered "splash pools" and hot tubs as ideal fish tanks for a long time.  As TcLynx said, you would have to hunt for and remove all metal fittings, and perhaps stand it outside with water in for a bit to see if it grows algae - a basic sign that any chlorine or other cleaning agent used in the previous phase of the tub is not still hanging around.

[David Waite]

I helped build a system with used bathtubs for grow beds and a hot tub for a tank. It works great. We fiberglassed over all the openings to solve the water tight problem. He has a 500 gal tank and 10 bath tub system for about 300 bucks in pumps and piping. Pretty cool.

[Rob C.]

Newbie question:  Why is fish water-to-metal contact bad?  Is it the potential for rust?  Or is it something far more sinister, like it creates giant, radioactive, mutant fish?

[David Waite]

Rob Galvanized pipe uses zinc to create the rust prevention properties. In a recirculating system zinc and copper can build up and become toxic to fish. Heavy metals or metals in general remain in the water column due to plants just dont absorb these metals to rid them in the water. Iron is the exception due to it becomes water soluble because of waters ability to break it down and plants use it as a source mineral. To be safe aquapons just avoid metals to be safe. Every metal is an alloy of several metals so you really dont know what it is made of.

[TCLynx]

Also, in Fish or hydroponics systems the water can tend to become corrosive to metals other than very high quality stainless steel and so those metals will not only corrode into the water (and be bad for the fish and possibly us when we eat the fish/veggies) but the materials will tend to fail before their time so you don't really want plumbing fittings that are going to fail installed in a difficult place to reach under a gravel bed or something.

[Rob C.]

Dang, I wanted giant, radioactive, mutant fish.

[TCLynx]

Well, those might be available from the oceans around the far east soon.