Jenny Molin

There are already some good answers that deal with the engineering challenges of using sea water however there's another big challenge that I think has been missed. Ocean water is full of all sorts of cute little crustacean critters that like to attach themselves to just about everything. If you used ocean water in toilets, you would have barnacles and other marine growth growing throughout the entire septic system. This would reduce flow and eventually clog it within a matter of a few years. And I do mean ALL parts of the system, from the holding tank on the back of your toilet to the outflow pipes at the very end. While having a coral reef growing in your house might sound nice, someone is going to have to clean out those pipes when they become clogged with marine growth and human waste - yuck!

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This actually does bring up an interesting possibility though. Perhaps marine growth that is usually seen as a detriment in plumbing such as at power plants, could be selected, or bio-engineered to effectively filter waste water. As the water progresses, slowly down the pipe or through a specially designed series of retention ponds it gets progressively cleaner by the actions of marine filter feeders.
https://toiletsguide.com/best-flushing-toilets/

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Generally the two best times of day are at dawn and dusk- as most fish species tend to be most active at this time. This can be partly attributed to activity of baitfish (small fish species that other bigger fish eat) as they tend to be most active around or after dark. Fish are also less vulnerable during dark hours to certain predators- like ospreys, that hunt during daylight hours. Another factor in that is water temperature; during the day with the sun high in the sky the upper layer of water tends to warm up, frequently beyond the "comfort zone" of many fish species (each species has a temperature range it favors), so some species will tend to "go deep" and spend the mid-day hours in cooler water under the cover of weeds, logs or just the water itself.
reference link: https://fisherreel.com/best-braided-fishing-line/

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