Daftboy, this is the 28 gallon tank correct?
"Set up. Fiji live rock,17 lbs, Live Sand,Canister:Fluval Multi-Stage 05 series 205,180GPH,T-8 over head single fluorescent 20w Pennplax FL20,150 watt heater"
Normally the "standard" for setting up a biofilter in a marine tank would be 1-1.5 lbs. per gallon of rock to allow for enough surface area for an effective biofilter. I would think the amount you have is at least about 10lbs. if not more too little.
Three fish in the tank are creating waste that is breaking down via the nitrogen cycle. You don't mention how much you are feeding them, also a waste producer.
You say you are cleaning the Fluval every 2 weeks. Can you elaborate some on the cleaning procedure you are using? In this tank it would seem that with the 2 week cleaning, the small amount of rockwork and the bioload that the filtermaterials would need to become part of the surface area required to have an effective bio filter. You may or may not be compromising this with the methodtime frame of cleaning. That is why I am asking you to go through you procedure with us.
The brown on the sand appears to be diatoms, an indicator in a tank that has been up since 18-Apr-2009 that there are excess nutrient in the system.
My feeling at this point is that;
You are under filtered for the bioload in the tank.
You have not struck a balance in water change schedules to accommodate the under filtering to remove the excess nutrient.
You may be overfeeding for the amount of livestock and biofiltering capability you have.
Your canister filter has become part of the bio filter as well as mechanical filter, is probably not being cleaned enough time wise, and depending on your answers may be being cleaned in a method that harms its bio filtering capability.
Snails die, especially margaritas as they are cooler water snails. I would think this to be unrelated to you issues with your dirty sand. I also believe that you are getting the ammonia reading because your test kit is old and the reagents are out of date, or the kit itself cannot read to degree necessary, or the color you may be trying to match is hard for the eye to calibrate to. What type of kit is it?
