Don't Starve Together Guides and Walkthroughs
Merm Farms are something that you shouldn't worry too much about until you get into the late game (day 500+). These farms will give you a good source of Freshwater Fish and Frog Legs as well as the occasional Bird Feather if you use Catapults like I do. In order to make a Merm Farm you will need to switch characters to Wurt since he can make the Craftsmerm Houses you need and you'll also need to switch to Winona to make the Catapults needed to take out the Merms. For these reasons it isn't really a good idea to do this farm early game.
Despite these drawbacks, if you are still interested in making this farm you'll want to start by taking out your Pitchfork and digging up a section of tiles big enough to house as many Merms as you want. In the picture above I have 12 Craftsmerm Houses which is about the minimum I would recommend you make. Once you have your swamp tiles down the next step is to create an invulnerable wall around the entire area.
This will be extremely time consuming and you (technically) don't need an invulnerable wall around the entire pen. In order to make an invulnerable wall you'll need to make statues like you see in my screenshot above, you can do this with the Potter's Wheel. My advice is to make a few Potter's Wheels or to move one around so that you spend less time carrying these statues. Another thing you could do is use Wolfgang who carries heavy objects faster.
If you look at my picture above you'll see that I am using Catapults to dispatch the Merms - when you make a farm like this Catapults are typically the best weapon to use against the monsters. What you want to do is lure all of the merms to one side of the pen (like you see above) and then unload on them with Catapults until they're all defeated.
Once this is done you can either move a statue temporarily so you can get into the pen (or) leave a small open hole in the back that you can get in and out of. Leaving an open hole is convenient but it will also lead to some Merms getting out of your pen occasionally (this happens sometimes too even without a hole due to this area of the world loading in and out).
<Bigger Merm Farm>
All in all, Merm farms are a great source of Freshwater Fish and Frog Legs - the biggest draw back to making one is the time cost and the resource cost. Since you will have to switch characters (at least) twice in order to make one you should really take into consideration if it's the right decision for you.
- add more about a big merm farm, like shown above
- add info about wrapping the food so it doesnt spoil
Other Tips & Tricks
