Mystery flies--help!!

[hermitsinnc]

About 2 weeks ago I made seafood stew for the crabs. It never molded, so I just left it in the tank (was planning to take it out this weekend). Today I opened the tank to discover swarms of tiny flying bugs on it (of course they dispersed before I could get a pic.) And since I haven't fed the crabs fruit in a couple weeks, I don't see how they could be fruit flies?

I have seen the what's that bug care sheet, but it wasn't helpful in identifying them. Fortunately, all 3 crabs are currently up, so they're having a bath in dechlorinated water for now. I have no iso set up yet, but I have a 3 gallon plastic tank, 10 gallon glass tank, and ~1 gallon kritter keeper that are all available. I have aquarium gravel, some sand (probably not 6 inches worth), and bricks of eco earth that I could use for sub. I have set up an ACV/dish soap trap but no bugs are in it yet.

What's the best course of action right now? Can the crabs go back in? If they need to be isolated, should that be together or separate? And how do I set up an ISO for healthy crabs?

I will upload pictures if I get any, but I've barely even seen the bugs.

Some other info that may not be relevant:
In the dish with the seafood stuff, I noticed what looked like isopods of some sort. They are not alive/responsive. (I will post a pic of those when I can get to my computer.) Not sure if they could be some sort of egg sac? Or molted bug exoskeleton?
The other thing they've been fed since the seafood is a mix I made in November with dried shrimp, cornmeal, leaf litter, and some other stuff. It has been stored in a glass jar at room temp. I have the exact recipe written down somewhere but can't locate it at the moment. I noticed small items in it that are either seeds or eggs--I don't recall what, if any, seeds were originally in it. And I fed the rest of the jar last night, so I can't compare. (Will post a pic of those soon too.)

[wodesorel]

It's going to be some sort of corpse fly. If they're the size of fruit flies then they'll likely be phorid flies, which eat dead or rotting things but are harmless to the crabs. The unmoving things are probably pupae, especially if they're brown in color, which are maggots that are transforming into flies - get those out of there quick and crush to destroy before they hatch. They'll be glued onto surfaces like the underside of the food bowl.

I've had full sized flies end up in my tank from forgotten fish before, holy heck was that NOT a fun time cleaning up because they hatched out before I noticed them and got into my house. You probably won't be able to trap what you have using the vinegar method (which works for flies that use decaying fruits for eggs) and instead will either need to physically crush them or use a commercial fly trap (which attracts meat loving flies) to lure them.

Phorrid flies do tend to self limit so long as there's nothing rotting to lay eggs in. You may get another burst of adults (can't remember how long their reproduction cycle is) as any maggots that crawled off hatch out. Try to keep the substrate relatively dry on the surface, limit wet leaves and moss, and change out food promptly for the next couple weeks and they'll move on to nastier patches.