If there are always particles in the water you are possibly not cleaning the gravel enough/properly, and as suggested get some finer filtration media for a start. I would also focus on gravel vaccing during water changes.
I would also change more water - what do your nitrates usually read at and how do you test btw - I would change 50% minimum - should be a breeze in a 30.
Those would address any acute difficulties regarding environment.
Medium term that tank is not going to be big enough for a happy population...I suspect your orange labs are actually zebras...they will kick the labs butts over time..if you're keeping the fish you need to focus on a larger tank - a 40G breeder (three foot long) would be a nice upgrade, a 55G would be even better and you could have a bunch more fish in there which would also help with their sociability. They like a lot of company but your tank is not big enough to support that.