The API kit will always read.25. I personally wouldn't even bother testing Ammonia nor Nitrites. They are very complicated to test for with hobby grade kits.
API is cheap and is known for false ammonia readings. For Phosphates I love my Hanna checker.
The HI774 Ultra Low Range Phosphate Checker® is a cost-effective way to measure phosphate in marine systems, including reef tanks. Excessive phosphate levels can prevent calcification, skeletal formation, and growth of many coral species, particularly those referred to as SPS or small-polyp...
www.bulkreefsupply.com
Don't let the price scare you, the reagents are only 9 bucks. It is super easy to do and read. I also use their Alk checker.
Why does BRS recommend this? The Hanna Alkalinity checker is an awesome little tool that now will give results in DKH values that are much more common in the aquarium hobby. It will also give you accurate easy to read results with the large LCD display. We like the repeatable results and ability...
www.bulkreefsupply.com
Once again, the reagents are only 9 bucks and super easy to use.
Keep up with the water changes, big ones won't affect your corrals. If the salinity and PH are the same you could do a 100% water change. Small ones weekly are much better for the snails and crabs though.
The nitrates are high. A fuge will help lower them, be sure to get a good light for it. Any grow light with a strong red spectrum should work. I use a cheap one off of
Amazon. The only problem with cheap ones is they will die sooner than an expensive one. Salt water is very cruel to electronics. The water changes will also lower the nitrates.
I don't know if a HOB fuge will fit on the tank. If it does I'd go with one of those. The bigger the fuge the better.
The perfect way to add a refugium to any sumpless aquarium! Refugiums can add a convenient and natural way to grow various types of macroalgae, which can significantly decrease dissolved wastes which might lead to algae blooms. At the same time, these small refugiums also provide a safe-haven...
www.bulkreefsupply.com
Black Friday is coming. If at all possible I would hang on until the week of Thanksgiving to purchase anything. Most everything will go on sale at some point during that week. A lot of these things never go on sale other than that week. Good luck and let me know if you have any more questions. I am always happy to help.