How to keep levels low?

[stanleo]

1) have a proper ratio of snails : hermitcrabs ..... 0.5snails : 1 hermitcrab PER GALLON

I read this yesterday and have been thinking about it and this seems like too many. When I was researching cleanup crews I found that a ratio of 1 snail and 1 hermit PER TEN GALLONS was the right number. When you have too many it can actually work against you because they won't have enough algae to sustain that big of a population and they die off, sometimes on mass. That can cause a nutrient spike which feeds the algae more. I have to say after 10 months I agree. I started with 10 snails and 10 hermits in my 120 gallon. 4 hermits died fairly quickly but I still have 6 and all 10 snails. I also have 3 emeralds and a long spine urchin that I have had for more than 6 months and the only place GHA grows is in my fuge. My NO3 is 2ppm and PO4 is .03ppm. My yellow tang does a job of algae control as well. If I were to follow the per gallon I would have had 200+ snails and 100+ hermits. I don't think they would last long at those numbers.

I have never used any chemical control or GFO for algae. My skimmer gets about a 1/2 cup of skimmate a week and I run a 10 gallon fuge with chaeto that I have to harvest once a month. I do biweekly 24 gallon water changes and I don't have any algae issues. I do get the film stuff on the glass and a brown algae that grows on the back wall that I just brush off every water change and that's it. I have learned that the brown algae grows in low nutrient environments but it grows slowly. By the time of my water change is when it gets really ugly back there so I don't worry about it too much. I feed twice a day and only enough so its gone in five minutes but i trust that some food gets into the nooks and crannys for the cleanup crews to get a taste. I also have thriving microfauna populations of copepods, amphipods, isopods and mysis shrimp.

I use Salifert test kits for NO3 and PO4 and I think they work great. I just do not want to spend the money on Hanna kits.

 

[ink]

I've been into this hobby for the last 20 years, and I have my third 1200 liters tanks that is 5y old. I often wonder what is wrong in me. I've never been able to have detectable nitrate (unless I dose sodium nitrate).
I struggle doing something in order to have detectable nitrate, but it always leads to SPS killing. I don't think I have much light, but If I reduce dramatically the light (I mean reducing from 18 to 10 54w T5 tubes, from 12h light to 6h light and raising fixtures from 2" to 10" above water), I start detecting nitrate, but just 0,2ppm. But corals growth becomes null.
If I increase feeding, SPS start having STN/RTN. Simply I can't find a solution.
Why I'm looking for nitrate presence? because I'm convinced corals growth in my tank is scarce and I see many SPS dominated tanks on forums whose owners declare to have high nitrate (>5ppm) and show pictures with substantial growth.

Really I can't understand how to have nitrate. Someone should find an explanation for me that I can't have it and for who has too much. I've been looking it for years and not yet found it.

Luca