Backyard Aquaponics
A place to discuss aquaponics

Sounds like the system is cycled. Your plants are probably just using the nitrates as fast as they are being produced. Mine runs with a lower pH than you have but all my other readings are usually zero, just like what you have.

Don't use the lime or lemon juice it has antibacterial properties. Most people just wait for the pH to come down on it's own and use chelated iron in the meantime. If you do decide to adjust the pH use HCl (Hydrochloric acid - aka Muriatic acid) and adjust the top up water, don't do the adjustment directly in the tank. Follow the instructions I already posted a few posts back

It is possible that the pH will not come down depending on how much buffering is in your water, just so you're aware - usually they come down within a couple of months but one of mine took 2 years.

Hope this helps

ok mate. i'll wait .. thks !!