I'm the worst at keeping it short... so here's the cliffs notes: I live it Houston, it usually does't get THAT cold down here, last year my 1500 gal pond's temp got to the high 50s at its coldest point, but this past weekend, the air temp was in the high 30s (coudlnt find the thermometer to check water temp) and my pacus almost died. Read on for the longer version. I'm sure you could heat a pond, but I'm also sure it would be super expensive to do.
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With the power out after the hurricane here, my biggest Pacu was dead when I returned to myhouse and the others (1 more red belly, 1 black pacu, and an Oscar) were looking really bad. I put them all out in my 1500 above ground pond on the deck, because even though there were no pumps working out there, I figured the bigger volume would give them the best chance to survive. They did fine out there, and seemed fine with the koi/goldfish as well. I talked to a coworker about leaving them out there for the winter and he said they woudlnt make it (I kept track last year, and I think the lowest the water temp got was in the high 50s).
Well, I decide to drain the tank and move it while the monsters are in the pond, plus they're doing fine, so I figure I'll bring them in 'one of these days'. It starts getting cooler, and I look and the oscar has a sort of sore on his head with a hazy film over it. I decide as soon as I get back in town (leaving for the weekend) I was going to set up their tank again, but when I got back he had died. the others seemed fine though. I feel like a bad fish-mom but I decided that I should let the other 2 stay out there and I was going to have the carpet changed as long as the tank was empty.
Over the weekend the temp got into the high 30s (wtf?? this is Texas?!?!?!) and I go to check on them, and the big silver pacy is upside down and looks dead, with the black one next to it, also looking dead (but right side up) I go to scoop them out, and they slowly swim off. I put them both in this big rubbermaid wheeled cart, about 1/4 full of the cold water, and wheel it inside, thinking I'm going to slowly siphon the warm indoor water into this, so they don't get shocked by the temp change (their tank isn't ready, so they're getting thrown in the other 150 gallon with all the cichlids). Well, as I add the water, they're starting to move aruond more, and the silver one turns right side up and starts swimming more normally. I feel brilliant, and am happy that I have saved my pacus (despite I was 'saving' them from my own neglect... but let's not dwell on that). Turns out I'm about as brilliant as that rubbermaid cart is watertight, so I end up with a saturated area rug, but two alive and back to normal pacus knocking everything over in my 'pretty' plants rocks and driftwood tank, it looks like a pair of giants in there,and the cichlids look very confused.
I really want to give them more room, and am toying with the idea of buidlng an indoor pond. How is the evaporation issue indoors? it would be in the 2 story vaulted living room. I'd rather build a huge tank with a viewing window, but the pond idea would be so much cheaper/easier. Any thoughts (and yes, I love the DIY section!!)