Why persistant traces of Nitrite?

[QuickCarl]

I constantly have low levels of nitrite 0.05 - .1 in my tank.
Specs:
Set up 15 mos.
F/O
Crushed coral substrate
probably 30 inches among 8 fish, plus 3 hermit crabs
very slight traces of ammonia if any, occasionally
Monthly 20% water changes with purified water
Substrate vacuumed bi-monthly
Wet Dry filter, prefilter and stand pipe filter cleaned bi-weekly
recently installed UV, (gave me crystal clear water, love it)
SG constant 1.022, nitrate .35 max
PH 8.1-8.2
Temp 84-85 (I know that's high, but I'm not buying a chiller)
I feed once per day.
Fish are all fine.
And that's it. I don't understand why I have nitrite with virtually 0 ammonia.

I also have a 20 gal q-tank that rarely registers nitrite. The only real difference between the two tanks is one is on another floor in the house and usually 5 -7 degrees cooler, and of course it has a lighter fish load.

Any thoughts on this appreciated.

 

[DragonMorayEels]

One thing or two I can say and one is I guess that you know that that sounds like a lot of fish in your tank but who am I too say.

But still on your water changes, I would do that on the weekly routine then monthly. For as well, your eight fish in all in this 75 and I have to guess that their not all fully grown as yet for the more fish you attempt to maintain only means that you much more foods in which case places you in a constant battle to maintain your tank. Perhaps you might consider in removing few fish?

You not mind the tanks temp high as that, I nothing other to add but then just maybe you want to try fans.