Couple of quick notes - Your Ammonia reading may be "throw off" by the fact that you still have nitrates present in your system. If you do a big water change (maybe 10 gal
or 15 gal
on your 29gal tank) then recheck N03 it should be quite a bit lower. AFter that I'd double check nh3
and you may see it drop.
Another thing with the kits, if its the "match the color to the card" type then they almost never read true zero - verify this by testing some bottled or RO
water sometime and see what it reads.
***Important regarding water changes*** do not add freshwater to your tank and then top off with salt solution (don't mix the salt in the tank itself). This is extremely stressfull to anything in there. Please please mix you saltwater in a bucket or clean/new trashcan and let it dissolve overnight. You can buy an extra powerhead and sit it in the trashcan to mix the water - or you can temporarily remove one of your powerheads from your tank.
I wouldn't sweat the PH
too much if you are going FO
. 7.8 isn't too bad and as quarryshark mentioned, adding new SW
will likely raise it slightly.
Last but not least - To answer your original question - after the water change and a re-test you should be ready to go.
hope this helps.