What do you mean they cant compete with loaches or catfish? I have cories, plec and coolie loach?
Shurley hel be fine with them if he has somewhere to hide?
It's nothing to do with hiding places. But cories, plecs, and loaches will likely eat the bloodworms before the spiny eel gets a chance. Of course, provide plenty of food, and you might be okay, but then you have the issue of water quality. So adding a spiny eel might work, but you have to watch that the spiny eel gets enough to eat. After suicidal leaps onto the carpet, the most common death for spiny eels is starvation.
Cheers, Neale