Thanks for a reply so far :) I got one whisper filter that said 10-20 gals and it turned out being too big for the tank, meaning it wouldn't hang on the edge because it was too long from top to bottom. I didn't realize they meant up to 10-20 gallons TALL tank! Yikes! That was my mistake, and now I cannot return it because the packaging was open (rgh), so they can't resell it online (i was mad at myself at that one, lol).
And as far as the heater goes, I did the same thing!! It is too long it ends up out of the the tank when it sits vertically.. I am so bad at judging the sizes of things apparently
, sigh.. heh.. I do not know if it would be just as good attaching it sideways in the tank (says it is ok to fully submerge), BUT I don't want to accidently cook my fish if it is wattage that determines how hot it will get.. it says it is 75 watts for an up to 25 gal. tank.
This is my 1st time doing this on my own so I guess it might take a few mess-ups before get a nice result. lol.. (i probably should have mentioned why I was asking my questions in the 1st place)