1) Is the proposed outdoor pond enough for 3 mature RES?
**They need 10 gal of water per inch of turtle & RES can grow to about 10"... so for 3 turtles you'd need about 300 gal - plus nesting grounds if you have female(s)
2) Should I transfer them to the bigger tank outdoors now?
**same answer as previous poster - NO glass tanks outdoors
3) How hot is too hot for the water temp?
**75-80 is good, you don't want to vary it too much. In the summer I have to add cooler water & more floating plants to my 125 gal pond (I'm in FL - the Tampa Bay area) to keep the temps right.
4) Do they really need that one plant (starts with an A) that kills algea?
**I don't know of any plant that 'kills' alge. Anacharis? Most turtles love to eat it and it's good for the water & cheap too ($2 or less for a bunch) but it's not necessary. My turtles like water hyacinth roots better, but they're banned in FL (too invasive). I use water lettuce & anacharis. I've heard it's best for a small pond to have 60-75% of the water surface covered, and I just add the surplus plant to my compost as they multiply. A little bit of
surface alge in an outdoor pond is GOING to happen. It's actually a good sign. I remove the alge "carpet" buildup from my waterfall every few weeks, but nowhere else do I have that much. Some gets on their basking rocks & a bit on the pond sides, but not enough to bother with. Actually, I've seen the turtles eat it where it grows dowin into the water from the falls. (Ugh!) Though I do have 2 large (12+") plecos that help, I'm sure.
5) If I transfer them to the bigger tank outdoors now with they be ok in 75 deg. water with weak sun for basking until I can set something better up or do I have to go full blown basking set-up now?
**Don't put them out in a glass tank - you can put them out for a while each day in a large plastic container w/ a makeshift basking area if you don't have the right lighting...but glass can cook them no matter how much coverage you provide. Where are you? Right now where I am the sun is still full strength & temps mid 80's. Depends on the weather if you can put them out or not.
6) Is it terrible that I want to toss a couple of small fish in there for food?
**not unless you expect them to live.

I use mosquito fish to eat the mosquito larve, and the turtles eat the fish. I also like to add cheap reddish "feeder fish" (NOT goldfish...little minnow-like fish) Most tuttles like the chase & some fish can give them excercise & amusement
7) Do they need the "muck" or can I keep the pond clear (if I can)
**Don't add anything to the pond 'muck-wise'. Some will build up on it's own, and unless you're trying to hibernate them (not a good idea!!) they don't need it. Some dirt will get in & sink, I don't usually bother it

WTH am I gonna do if my siblings have babies? Are they going to have two heads?
**Dunno - prev poster says no. I assume it happens in the wild though...
9) Anything I should NOT plant around or in the pond?
**I ran a search on plants poisonous to turtles before digging my pond & got some surprises, like marigolds. Pothos (philodenderon) are poison too, but I can't remember most of them. Do a search before planting the area where your guys will have access. ~~I recommend a hibiscus personally. Mine like the flowers as an occassional treat, and the shrub can be kept pruned small & low for them to hide under when out of the water.
10) The only thing I use now is Stress Coat and prefiltered water. Can I keep doing that?
**When I do water changes I just use regular water from the hose & add either stress coat (has dechlorinator) or regular dechlorinator. Haven't had any problems, but I've not researched that road....
11) When they are ponded do I still pull them to feed AM and PM pellets and vegtables in a seperate container, or do you toss food in and skim? I'd hate to turn them feral through noncontact... these are our babies babies.
**I feed pellets to mine every other day - I'll hand feed the first few, and dump in the rest. I've learned to gauge how many to feed & any leftovers will get taken care of by the minnows & 2 plecos (bottom feeders) I have in there. Mercer likes to scavenge the bottom for sunken pellets too. I feed their veggies daily. Liza begs as soon as someone walks by - no matter what. You'll still have plenty chances to handle them, don't worry!
12) One of these pups might bite us one day, how bad is it going to hurt?
**Liza is nearly 9" now (penn cooter - she'll grow to over a foot long) and enjoys being hand feed. She gets my thumb fairly often, and sometimes even shakes it like a shark trying to get the food. So far no blood - not even bad pain. She's gotten my 4 yr old while hand-feeding too, and the kiddo laughs it off. That's not to say a bad bite won't happen - I'm just saying a bite is not always a horrid experience. I wouldn't try hand feeding a known 'biter' though.

That's just askin' for it! Handle them with care!
13) I'd LOVE to go Alternative Energy! I've looked and talked to a few people with fish ponds and so far I get that they just don't perform. Does anyone have amn alternative energy set up that does?
**No idea.
You said your turts are about 1.5" - 3" now? Just curious, but are you measuring from the front of the shell to the back?...cause I'd be very hesitant to put any turtle under about 3+" outdoors w/o a VERY safe enclosure. Raccoons, cats, dogs will all be curious. I've even seen large egrets fishing in our pond. And you'd have to be pretty careful if you want them to remain outside all winter. I'm in central FL and it can be done here (with lots of care!), but I imagine any further north at all & they'd have to be brought in for a few months at least.
Here's my pond area, though I'm getting ready to expand the fenced land area around the pond to accommodate a larger nesting site:
http://www.redearslider.com/forum/viewtopic.php?t=12418
(the pond pics are below the ones of my son's new hatchling) You can see the alge on the large 'white' center rock & the waterfall