Sump help

[Cole.mormon]

Is this ok to use for an adapter

 

[xxkenny90xx]

No, find something plastic

 

[KrisReef]

For a horse trough, yes, but for a reef tank no. That galvanized pipe will corrode quickly. I think that it will add zinc, iron, and other pollution that won't harm a horse but may kill coral and fish?

You need a plastic pipe reducer, like @xxkenny90xx pointed out.