I am hoping someone has an idea that I haven't thought of with this problem:

In brief the parameters are as follows:
Nitrate between 2.5 and 5 ppm
Phosphate <0.1ppm
Calc 410 mg/l
Alk 3.66
Mag 1140 which is a little low prefer to have this up around 1350-1500 but I don't think this level is detrimental.

I use RO water mixed with reef crystals.

The tank is 255 litres with an upflow sump measuring 33" x 6" x 9" this contains a DSB that is about 6-7" deep above this I have caulerpa growing which covers the DSB I remove half of the caulerpa when the water surface is completly covered and I remove it from alternate ends to keep it as fresh as possible this is lit 24 hours a day by a single marine white flourescent T8. The over flow weir has a bag of phosphate remover in it.

The main tank also has a deltec mce 300 skimmer and I utilise an eheim 2215 to run an 8 watt UV sterilizer the eheim has no media in it. It also has a couple of powerheads the water turnover rate is about 25 times per hour.

It also has 30 kilos approx of premium and ultra grade live rock from stm the tank has been running for over 7 years but in its current set up for about 3 years. Prior to this it ran with a fluval external with ehfi substrat I'm sure you can imagine how demanding nitrates use to be. When this was removed the upstream sump was added. Nitrates ceased to be a problem within 2 months even on a test run I managed 6 months with out a water change as a test of the effectiveness, it was monitored very closely! Nitrate peaked at around 10-15 ppm if I remember correctly.

It is lit by 2 150 watt metal halides for about 7 hours a day the bulbs are 50,000 k and are about 9 months old.

Stock consists of the following:
80 micro dwarf blue leg hermits
a few red leg hermits
6 black foot turbos
1 cleaner shrimp
3 true peppermint shrimp
1 serpeant star
1 blue linkia
A couple of corals button polyps and mushroom nems etc
1 Coral Beauty (about 7 years old)
1 Fox face
6 neon chromis
pair banggai cardinals
pair black percs
1 pyjama wrasse

I am going to add some giant turbos and I am also going to get some gubbins to convert a maxi jet pump into a stream pump so I can have 2 stream pumps in the tank instead of the one I think that will up my flow rate by about 7,000 lph. This will give me a tank turnover rate of about 50 times per hour!!!!

Does anyone have any ideas and I'm not stocking a tang I don't have quarantine facilities and last time I got a tang I had an Ich out break the only survivor was the coral beauty. I like tangs to look at but I don't like keeping them!!!!!

Are there any grazers you can suggest invert or fish or am I missing something obvious?

Maintenance regime is a 15% water change weekly to maintain calc and alk and dosage with kent super dkh and seachem pro calcium as needed. Every couple of months half of the caulerpa is removed or when there is insufficient room for growth plus phosphate remover is replaced approx once a month or when phosphate levels start to climb. Periodically I also throw a bag of carbon in to remove organics but I prefer not to leave this in too long.

Cheers in advance of all of your help.

__________________
Alan

Thweeerp!