am with others 25hp min, though be nice to see you with 30HP. 25hp is still in SCUT (sub compact utilty range), and getting up to 30HP tends to get you into CUT (compact utilty tractor) range of tractors. the difference...
scut = riding lawn mower on steroids, with pure basic 3pt hitch. FEL = anything better than manual shoveling.
cut = get away from riding lawn mower frame, a heavier tractor, split rear brakes on opposite foot than the gas/go/hst peddle. more lift capacity of FEL and 3pt hitch. more ground clearance between bottom of tractor and the ground. there tends to be a bit more functions for FEL and 3pt hitch as far as valves go. and more likely more ranges / gears to choose from (instead of low/high, low/med/high) for better getting what MPH / ground speed you want.
your acreage to mow is not that big so 25hp is fine, but you have a lot of little things. maintenance wise, that will come up. and having a little more tractor would not harm you mowing, but help you with all the little maintenance of property things that come up.
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your FEL lifting capacity.... if you are bring in any sort of "pallet stuff" perhaps feed for horses that comes in bags on a pallet. or you wanting to load/unload something into a truck / trailer having both FEL lifting height and capacity maybe an issue for you.
example concrete bricks, concrete bags, for the pond, any sort of lumber, moving dirt you remove from digging pond. into a dumpster. large round bails.
FEL (front end loaders) are not the best at digging, a tooth bar (strap on, bolt on) can make digging with FEL easier. but still not the best. a backhoe on tractor or better yet a mini ex or excavator much better in maneuvering and getting into areas, and just overall time spent digging and placing dirt you remove.
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Koiphen.com = koi/goldfish ponds and filtration for them. head over there for your pond. read up on the many DIY builds there. along with DIY filtration.
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you can get a backhoe with purchase, and tends to be cheaper if you buy... tractor, FEL (front end loader), cab, backhoe all on same receipt. but it does not sound like you will need a backhoe. and you would most likely be better off "renting" or pay someone else to dig and then do cleanup work with your unit.
many folks do the "save all the odd jobs" and then go rent an mini excavator for a weekend or like thing. some folks need a backhoe. your acreage so small overall. that you would not have any other use for an actual backhoe. and better off spending the few thousand bucks for a backhoe, in just renting a machine, and spending rest of cash on other stuff.
the exception to above. is you really do plan on DIY the entire pond yourself. including digging out the hole, running all your pipe work and digging holes for filters. if that is it. then a backhoe would more likely pay for itself. just by having it on hand when ever you got time to work on the building the pond. but even then. being able to rent a much larger mini ex (mini excavator) or larger excavator....
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TNT (top and tilt) for 3pt hitch, you really do not have a long driveway, and acerage is small. so the little amount you may need to adjust the 3pt hitch lower lift arms or top link for 3pt hitch. you most likely already done, and just a little work with a metal garden rake or shovel and would be done.
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you might see upper lights, on cab, sun shade, or ROPS (roll over protection system). be worth there time for you. both point frontwards and backwards.
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with above said, you will most likely end up spending a descent amount of various attachments for the tractor.
a good spot for newbies =
Tractor Attachments And Skid Steer Attachments For Any Tractor Or Skid Steer = watch the videos in setting stuff up and using it. to get yourself familer with what is out there.