This achievement requires you to have 10 different types of largos at the same time. A largo is a slime that has consumed a plort that is not of their species. (i.e. a rock slime eats a pink plort). DO NOT make a largo eat a third random plort as this will make it become a tarr and attack you.
The easiest way to do this is by loading up a new world. Do not worry about the pink and rock slime for now, as they are very close to the farm. Your first step is to amass a bunch of food. Chickens, vegetables, and fruit. You want to go past your ranch and drop to the left where you will see a giant pink slime. feed it until it bursts and pick up the slime key.
Now go to the left from the area with the water source (there will be a pink tube to walk through). Run to the tree and turn right until you see a bridge. Run through and you'll be lead to a door. Open this with the slime key. (make sure you have jetpack. it is important.) Run into the moss blanket (an achievement will pop if you have not gotten one).
While inside the moss blanket, you will need to pick up a few boom and honey slime. If you want this to go by faster, pick up a mint mango or two for the honey slime. Now return home and drop them off but DO NOT feed them. Run around and pick up some Pink, Rock, and Tabby slimes. Also some food. vegetables or meat preferred. Boom and Tabby eat meat. Rock eats vegetables. Pink eats anything.)
Now it should be around night time, so if you want this with less (or more) hassle, pick up the phosphor slime so you have more options. Now Put all the slimes down and take one breed into a corner and feed them some food to get plort (Get 5 or so.) Now start throwing the plorts to the other slime species until you hit the 10 mark and get the achievement! Enjoy the 30 Gamer score. I will leave a list of the slimes and the possible combinations.
Pink (eats anything)
Rock (eats vegetables)
Tabby (eats meats)
Phosphor (eats fruits)
Boom (eats meats)
Honey (eats fruits)
Pink Rock, Pink Tabby, Pink Phosphor, Pink boom, Pink Honey
Rock Tabby, Rock Phosphor, Rock boom, Rock Honey
Tabby Phosphor, Tabby boom, Tabby Honey
Phosphor boom, Phosphor Honey.
If you have any problems or any way to make this achievement easier, just leave a comment. Happy ranching!