Questions On Pacman Frogs

[Zofia]

Hi! Personally I'd recommend a lamp and heat bulb over an undertank heater. Side mounted I find they don't transmit heat very well, and heating on the bottom for a frog is different from natural conditions, since Pacman frogs burrow to escape heat.

But I heard it could burn them because of the short area between them and the heat, but I will definitely look into lamps!

The eco earth ( coco fibre ) is safe and is fine to use, it wont hurt your frog. I have kept all my Pacman Frogs on this for years and have had no issues, and tons of other people use it also with no ill effect.
For the heat matt you are better off getting a bulb for overhead heating. The heat matt doesn't do much on the side and putting on the bottom is making them do the total opposite of what they want to do. They burrow during the day to get out of the heat and direct sunlight ( to keep cool ) and to keep hidden from daytime predators. They don't burrow to warm up. Heat comes from the sun not the ground. And you shouldn't cover more then half the bottom when placing it on the bottom because they need to be able to thermoregulate there body temps if need be, so you need a hot a cold side. And at night they need a temp drop.
The R/O water shouldn't be used to expand the substrate or for the water bowl, there is nothing in it mineral wise and the frog needs these minerals and stuff to stay healthy. The R/O water will leach these minerals out of the frog and could eventually make him ill. Even my exotic vet here were I live has told me not use R/O or distilled for these reasons. R/O is good for misting because it so pure it doesn't leave spots all over the glass. You want to use tap water with a declorinator or some spring water. The water conditioner you have should be ok, lots of people use these fish brands with there frogs with o problems.
The crickets as mentioned above will do just make sure you gut load them and dust them with vitamins and you will need to give him other things as treats to vary his diet, hornworms, silkworms, butterworms waxworms, phoenix worms are examples of good treats. The night crawlers are better for a staple and more healthy for him then the crickets, you can really notice the growth rate change once you introduce them into the diet. Also another thing you can feed as a staple because you live in the U.S and can get them are roaches, again these are better then crickets. And don't feed to many mice for the reasons stated above.

What do you mean by R/O water? I plan on just dechlorinating all the water I use to mist and put it the dish..

And one more thing, if you get a baby I wouldn't put it in the 20 gallon long right away because it will be overwhelming for him and stress him out. 20 gallon longs are usually recommended for big adult females or if you end up with a big male. Most people start there babies off in a critter keeper and move up from that. What you could do though is put a divider in the 20 gallon long, make so its about the size of a 5 gallon and move the divider as he grows to give him more room. This is the method I use so I don't need to buy a ton of different size tanks.

Definitely going block off a lot of the tank when I first get him/her thanks!