First off, the reason for doing this extreme husbandry is because seahorses affinity for bacterial infection caused by nasty bacteria like vibriosis types and others. These nasty bacteria get to plaque levels as far as seahorses are concerned when temperatures are above 74°F and when they have food and bedding. This food and bedding is the uneaten food and food waste detritus that is decaying either trapped in the tank somewhere, or caught in the mechanical filters. This deterioration of water quality happens before it ever gets to the nitrate stage, and, there are NO hobbyist test kits to tell you when it gets to problem levels so preventive maintenance is needed. It may take many months before the problem arises as the water can degrade slowly or fast depending on tank conditions and cleaning habits.
I would never go more than two weeks without a large water change but prefer more often based on my years of experience good and bad. More important is the removal of any uneaten food and detritus before it decays.
Other marine fish don't have this problem so you wouldn't normally have to worry about it for a fish only or reef tank.
In a seahorse tank, the pods would quickly become decimated so in fact you would need to culture them outside the tank and add when available. They ARE and excellent food, but unless you're going to have an extensively large or multiple set ups it can't be the primary food source. I don't know of anyone in my years of keeping that anyone has managed this long term.
Brine shrimp (artemia) can be a useful tool to get nutrition to the seahorses. However, unlike a mandarin, the artemia need to be grown out to adults before being enriched with a high DHA product. Most seahores other than dwarfs, can't be bothered with small shrimp like a mandarin eats, especially as they become adults, and, they would have to consume an inordinate amount of them to be of any value at all. I personally restrict the brine shrimp feedings I do to about once a week, with frozen Hikari mysis being used as the main food.
I used to grow copepods to augment the nutrition, but after a few years it became to much of a PITA so I just kept on with the growing of artemia that I'd been doing for over a decade at that point. (I grow them out in 26g rubbermaid containers)
I use phyto for the first week or so of the nauplii stage of brine, followed by greenwater made from well blended spirulina powder and then enriched at the adult stage using well blended Algamac 3050, high DHA, even higher than high DHA selcon. (I'm not partial to selcon/selco as being an emulsion, deteriorates rapidly, whereas the 3050 is a powder and can be kept long term in a freezer)
Growing Brine Shrimp to Adult
Also, nutritionally, brine shrimp are NOT sufficient for seahorses full time.
A further problem with live food feeding is that if for some reason the supply became blocked for a bit, the seahorses by that time will no longer consume frozen foods, and seahorses, when going without food for around 4 days, may never start to feed again and need to be tube fed with a syringe and cannula.
You may want to reconsider getting into the hobby if you have to carry water from the basement to the second floor all the time as the amount and frequency can burn you out in time, leaving the problems that arise from gradual slackening to cause fatalities.
I have some of my tanks on the first floor and for years carried the water upstairs and eventually I had the burnout and losses. I finally got a hose long enough to go from the mixing tanks and water holding tanks, up to the tanks on the first floor so I didn't have to carry it anymore. At my age it's a real challenge. I also use the hose to service all the tanks in the basement, but they were not as much of a problem as upstairs because I used a dolly cart to move the pails of water. The hose works out much faster though.