In the wild you find
Tigriopus californicus in splash pools in rocky intertidal habitats well above the waterline. So there is rarely, if ever, a direct connection to the ocean. Whatever water movement there is comes usually only from the wind, which is why I keep my cultures on the balcony.
Temperature and salinity swings are usually well tolerated. I recovered cultures that had evaporated to salinities over 1.050 by just dumping freshwater in.
I usually harvest with a fine fish net, but dumping through a fine Artemia salina nauplii harvesting sieve will work too. Usually the culture peaks after about a month. At that point you can harvest all and use a part to start a new culture. I usually let them run until the culture starts slowing down. Though even such a culture can bounce back.
You will see a lot of sludge accumulating on the bottom - that's not bad at all but rather beneficial. I usually don't find many nauplii in the water so I suspect they like to dwell in the sludge.