no worries .. just keep asking til you understood.

make sure you stock up a lot of tadpoles & froglets. It's easier to attract bottom dwellers without any interruptions from the frogs.
from spidercrab, shrimp til starfish, the most successful attraction by planting all the deterrents (corals plus dulcia), otherwise it's really difficult to attract ..

Hiii Adeline, .. better do the frog breeding first ..
land frogs are for back up. It's easier if we can attract in under water straight away.

Fox x
Tortoise x
Mole x
Brown Bunny x
Grey Squirrel x
Red Squirrel
Wren x
Yellow Wagtail x
Chaffinch x
Raccoon x
Hare x
Singing Bush Lark x
Skunk x
Gecko x
Meerkat
Camel
Piglet
Donkey x
Bee Eater
Olinguito x
Cuckoo x
Deer x
Kiwi x
Chipmunk
Coyote
Pink Fairy Armadillo
Wolf
Hedgehog x
Waxwing x
Lop Eared Bunny
Porcupine
Roadrunner
Armadillo
Ostrich x
Badger
Nightingale x
Elephant x
Guinea Pig x

Goodnight Adeline sweet dreams xx

once you started doing it, then you'll get a better understanding about the frogs.

the frog family sets that you spot in other gardens will turn into LAND FROGS.
the 5th land frog will leave you spawns on land, then you have to attract mermaid.

For breeding underwater frogs =
the cycle is from
tadpole turn into froglet and then Adult frog.
it's a multiplication of 5 (set of 5 family frog) =
so every 5, 15, 55, 85, 115 ..
the 5th Adult frog will give you spawns

if you've attracted ghostly frogs in your garden, they need to be added into the total adult frog calculation

try to farm the frogs before you start the bottom dwellers. I normally attract tadpoles together with froglets, and only attract the adult frogs when I need them.

for the maximum attraction & best result of bottom dwellers you may want to plant dulcia to deter frogs. 
there're others who don't mind the frogs, so they'll attract both altogether.

the low level bottom dwellers stay for max 15 mins on organic food / 30 mins on super.

high level bottom dwellers need other corals to deter the low level bottom dwellers. they're rare to attract & without other corals, it's just entirely based on luck.

mermaid will be RTH in 1.5 day & coral about 2.5 day.

frog breeding first.
by the time you're ready to attract bottom dwellers, it's good if u only need 1x adult frog that drops spawns

nitee Adeline, it's getting pretty late in here

yes, you can start by attracting 2 land frogs, the 2nd one will lay spawns for you.

basically, the ones that you spot in other gardens will give you land frogs to lay spawns ;

and the UW frog families that you attract in your own garden will give you UW spawns.

it's a set of 5
every 5,10,15,20,25, .. adult frogs (either  land or UW) will lay spawns

the 5th land frog will lay spawns for you, after you have spotted another froglets in other gardens.

Try to spot more tadpoles & froglets.
From tadpoles -- froglets -- then into adult frogs