Freshwater items used in Saltwater?

As long as copper wasn't used I'd say it would all be pretty safe.

 

Make sure any pumps you use do not have iron parts that could rust and kill everything. Most powerheads and power filter pumps are ok. Some external pumps (mainly older models)  may have the iron parts in them. Make sure you test all equipment with a spare tank or bucket before you use with equipment that currently contains or that will contain livestock to prevent contamination. Also, do the sniff test on the equipment you plan to use, if it smells burnt, use caution when testing if you choose to try and use it anyways.
The AC30s should be fine, the titanium heater should be fine, but i would test it to make sure that it is operating properly aka it keeps proper temp consistently, and that the thermostat is not bad, where the heater turns on but will not turn off when it reaches desired temp but continues to rise and cook your tank. If you have chemicals and bio materials you are concerned about, read the directions, most will say if you cannot use in SW or FW. If you cant find anything on the labels, google it, or ask on here, there is bound to be someone who knows what the product is. Goodluck