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    <p>After rereading the question, I think the simple answer is to use <a href="http://hackage.haskell.org/packages/archive/lifted-base/0.2.0.2/doc/html/Control-Exception-Lifted.html#v%3abracket" rel="nofollow">a lifted bracket</a>, which will handle all of the transformer issues. I'll leave my original answer as well, as it might give a bit more insight into what's happening.</p> <hr> <p>The problem in this case is the usage of <code>liftIO</code>. Let's look at the type signature:</p> <pre><code>liftIO :: MonadIO m =&gt; IO a -&gt; m a </code></pre> <p>What this means is that you can take an arbitrary I/O action (e.g., reading from a file) and run it in any monad which allows I/O to be performed, such as the database monad. However, what you're trying to do is really the opposite: run a database monad action as just a normal I/O action. This can't be directly done, since the database actions rely on extra context- specifically a database connection- which the <code>IO</code> monad doesn't provide.</p> <p>So how do you turn a database action into an IO action? We have to <em>unwrap</em>. Unwrapping is a common activity for <em>monad transformers</em>, which can be thought of as layers added on top of each other. Lifting (as in <code>liftIO</code>) allows you to take an action from a lower layer and move it up to a higher layer. Unwrapping takes a layer off. Since how you unwrap depends on the specific transformer, each transformer has its own unwrap functions.</p> <p>In the case of Persistent, you can use withSqliteConn or the equivalent for your backend, see the synopsis in the <a href="http://www.yesodweb.com/book/persistent" rel="nofollow">Persistent chapter</a> for more details.</p>
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    1. COThanks for the clues. I removed the `liftIO` calls and am using the lifted `bracket`, but I'm still having trouble. I think one of the clues I need is the type signature of withYellowfinTuna. I know it's not supposed to be `FishId -> PersistMonadBackend ()`, but I can't figure out what it *is* supposed to be! I should probably also say that I'd rather mention I'd rather avoid using database-specific calls such as `withSqliteConn` whenever possible. Unfortunately, though, the relationship between `runDB`, `withSqliteConn`, and `runSqlConn` is not quite clear to me, yet.
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    2. COI've updated my original post with where I ended up after reading your answer, but I am still stuck. I'm having trouble figuring this out, I think, because I don't know the type signatures of `insert` and `delete` in the context of my `Fish` model. Also, is it actually appropriate for me to call `runDB` in these places, and why? I don't know why my return type is `OneSpec Connection ()` after calling `runDB`, but it's what the compile errors told me to use!
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