1. If I channel to make an artificial underground canal or pool, fed by a natural river (and disappearing at the edge of the map), is there a chance small fish (as I understand it, vermin) will populate the canal so that I can fish from it?

  2. What if I let the water run through floor grates or wall grates to keep out crocodiles? As I understand it, this will definitely keep out large fish (creatures, as opposed to vermin) like carps. But what about small fish? I.e. do vermin pass through the floor grates? Or, on the other hand is it possible that the small fish will spontaneously spawn in my artificial pool/canal?

Of course I could build a walled off area with floorgrates over the river, this would let my fisherman fish safely as well. but it's less beautiful and I thought the grate over the river would be more vulnerable to building destroyers.

  • As I understand it, building destroyers have to be adjacent to break things, so a grate above them should be safe. Sep 25, 2011 at 3:39
  • Building destroyers are supposed to be able to break grates above them, but it's currently bugged so they cannot. They can still break downward, just not upward.
    – Paul Z
    Sep 25, 2011 at 7:56
  • well they would also have to be swimming while they break a grate above a river, which is i guess not impossible. But: what about my original questions? Does nobondy know?
    – relatively
    Sep 25, 2011 at 20:17
  • It is amazing that no-one knows the answer ;) I have in the meantime constructed two indoor pools fed by a river, one of them behind a grate - we will soon know something more about the probability of fish spawning there! Although I'm not enough of an expert to work it out in Bayseian terms...
    – relatively
    Oct 1, 2011 at 18:50
  • 1
    So! If the indoor pool is behind a grate or fortification, there is no fishing (It says "Fishing (0)" in the zone menu right from the start. The artificial pool without grates DOES support a fishing zone, but I can't say yet if anything is being caught there. Investigation is ongoing.
    – relatively
    Oct 10, 2011 at 10:45

4 Answers 4

  1. Yes, water creatures can swim from natural rivers into any connected bodies of water including those dug out by your dwarves.
  2. I believe bars, grates and fortifications all let water flow but keep creatures out, including vermin at present*. The idea for allowing vermin/small creatures to pass through bars (but not grates) has been floated in the past, but to my knowledge this has never been implemented.

Also note this bug: dwarves and creatures can sometimes be pushed through grates/bars/fortifications by water flow, though in my experience this is pretty rare.

*EDIT: @Daenthy correctly notes that vermin can spawn spontaneously in habitats that support them, so vermin may still turn up in your "secure" water sources.

  • can creatures like vermin go through pumps?
    – Fennekin
    Sep 21, 2015 at 8:26
  • I don't know, but check the answer from @Daenyth below. I would assume only fluids would be drawn up through pumps, but wouldn't rely on that. Given that vermin can indeed spawn spontaneously in habitats that support them, I would assume they could turn up on the other side of a pump stack (or indeed your grates etc - I'll update my answer).
    – raveturned
    Sep 22, 2015 at 11:11

Vermin appear randomly in any tile that can support them. There's no way to prevent it.


As of DF 0.40.23 I'm getting salmons in a channel that is fed from a river through a grate. I cannot set up a fishing zone near the channel (don't know if it's a bug or a feature) but the salmons are definitely there.


No, I'm almost certain that won't happen. I believe fish will only swim in the river, stream, moat, etc. that they're supposed to be in and where the game designers put them. It's not like the fish will understand there's more water over there and try to swim to your spot.

  • Rats seem to understand that there's more land when you dig out something and go there, so it makes sense that fish would wander similarly. Nov 24, 2011 at 19:24
  • 3
    -1, this is just speculation.
    – user7220
    Feb 22, 2012 at 8:57

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