All of your aquarium parameters look great for a new aquarium that is cycling, and it’s possible that your biological filtration may have completed the cycling process, especially if you are using live rock and live sand. As you know, the porous interior of pre-cured live rock houses a considerable population of both aerobic nitrifying bacteria and anaerobic denitrifying bacteria, and this can provide the aquarium with some limited instant biological filtration ability and therefore help accelerate the cycling process. Live sand likewise contains both Nitrobacter and Nitrosomonas nitrifying bacteria, which helps speed up the nitrogen cycle by providing the necessary "seed" bacteria to kickstart the whole cycling process. But the use of live rock and live sand, or pre-aged saltwater, will not eliminate the need to cycle your aquarium entirely. You will still need to provide a source of ammonia to feed the beneficial bacteria and build up a sufficient population of the "good guys" in order to handle all the wastes produced by your seahorses, and you will have to monitor the aquarium closely while it cycles in order to determine when the process is complete.
So, if you have been feeding the nitrifying bacteria in your biofilter by providing them with a source of ammonia — say hardy, expendable fish such as damsels or mollies, for example, or perhaps decaying cocktail shrimp instead — or adding the ammonia directly yourself, drop by drop, and your ammonia and nitrite readings are at zero, then it sounds like your aquarium has indeed cycled and is ready for the cleanup crew.
But if you have not been providing a substantial source of ammonia for your newly established aquarium, the ammonia and nitrite readings are staying at zero simply because there is no bioload — nothing to produce ammonia in the first place. In that case, the cycling process really has yet to begin.
You are quite correct, sir — you want to see a nice high ammonia peak when first cycling your aquarium in order to build up a large population of the Nitrosomonas bacteria that feed on the ammonia, followed by a correspondingly high spike in the nitrite levels to promote a large population of the Nitrobacters that consume the nitrite. So you don’t want to do anything that will reduce the levels of ammonia and/or nitrite in your aquarium while the population of beneficial nitrifying bacteria is becoming established.
Take care not do anything to remove ammonia and/or nitrate from your aquarium while it is cycling initially and the biofiltration is becoming established. No chemical filtration media of any kind, including nitrate absorbers, should be used while the aquarium cycles, nor should you perform water changes or operate your protein skimmer or ultraviolet sterilizer until the cycling process has been completed. Protein skimming, UV, water changes, and the use of chemical filtration media can actually prolong the cycling process and reduce the numbers of beneficial nitrifying bacteria that build up by depriving them of food.
In short, if you can advise me what sort of ammonia source you are using to feed your beneficial nitrifying bacteria, then I can give you a better idea of how far along your cycling process is and how much longer you may have to wait before the biological filtration is fully established and you can begin stocking the tank.
Low levels of nitrates are harmless to marine fish in general, including seahorses. We want the nitrates to remain below 20 ppm in our seahorse tanks at all times, and ideally below 10 ppm, if possible. But providing you won’t be keeping live corals that are compatible with seahorses in your aquarium, then you normally needn’t be concerned about monitoring nitrates at the low end of the range. Once your aquarium has cycled and the biofiltration is fully established, you only need to test the nitrates to make sure that they remain between 10-20 ppm. However, while the aquarium is cycling, testing nitrates in the low end of their range can give you an idea of when the Nitrobacter population is peaking and converting all of the available nitrite into nitrate, so it’s a good idea to check low end nitrates during the cycling process for this reason.
Best of luck cycling your new aquarium, arcprolife! Get back to me as soon as possible regarding the source of ammonia you are providing, and we’ll have a much better idea of how things are progressing.