Tank Smells a Little Fishy

[gregzz4]

I gotta say it's probably the lack of carbon use
It removes all kinds of organics

Carbon is used in lots of air quality filters

Go back to using it in the proper amount and you probably will find the smell goes away

[gregzz4]

You say you stopped using carbon due to your corals ...

Is it possible you were using too much, or your method was allowing it to get into your DT ?
Carbon getting past your method can cause all kinds of issues in your tank
Just trying to help

Check out the BRS calculator thingy for how much to use ...

Select the Carbon Calculator, enter your water volume, select your kind of carbon and click 'Calculate'

Keep in mind one thing ....

I have a 75g with a 50g sump (total 125g potential water), but I only have 110g of total water in my system

Keep this in mind when you calculate your system volume