Nitrate at 15-20

[Fig]

I have my main 30 cube tank with virtually undetectable nitrates and my corals are colorful, but the frags from those corals look better in my frag tank with nitrates of 15-20. Alk/cal are at 9-480 in both tanks. Phosphates are at 0 according to a API test kit but knows what they are at, but I run GFO in a reactor in both tanks and have no undesirable algae in both tanks. I certainly don't want them to get any higher but am happy to see the corals color get better and perhaps think I'm under feeding my 30 cube at the moment.

[bertoni]

Well, since the nitrate is zero, you could try bumping up the feeding a bit. I'd be very careful about watching the phosphate and nitrate, though.

Is the lighting similar?

[Fig]

I've thought about that aspect to. I'm running a 175 watt Iwasaki 15k on the 30 cube. Prior it was a 250 watt Reeflux 12k. On the frag tank its been a 250 watt AquaMaxx 14k from the start. I guess I'm just a bit surprised at how good they look at 15-20 ppm of nitrate. I've siphoned out sump and pulled out alot of gunk on the frag tank and harvested some chaeto as it was pretty thick.

[HighlandReefer]

It could be the difference in lighting and water depth.

I would not let your nitrate level get higher. Research has indicated that levels in excess of around 20-30 ppm nitrate can cause problems for many coral.

[Fig]

I won't let them get any higher. But I don't think I'll strive for 0 anymore.