how do i know if i have a nutrient issue.what test kits are accurate right now phosphate and nitrate are very low almost 0.i only feed once a day frozen food and not very much.my sand bed is about 2 to 3 inches deep.
If you have excess nuisance algea growth then you have excess nutrients. It's that simple.
Forget the test kits. If you really want to get more accurate numbers you can buy a photometer for nitrate and phosphate detection, but they are also slightly inaccurate at low levels (but far better than any other hobby grade kit). Even if you find out what the exact levels are, the treatment suggestions aren't going to change much. Regardless of what any test kit tells you, the treatment for excess nutrients will be pretty much the same.
Frozen food preservatives are contained in many frozen food preperations. Foods like frozen mysis and frozen brine are best if they are rinsed before use becuase that rinses off the perservatives or gel binders which often contain lot's of phosphate. Foods like rods food or formula one, which are a mixture of various foods, should not be rinsed because you will wash away many of the small foods contained in the mixture.
Do a simple test on your sand bed. Stir up a small portion and see if a lot of dust and detritus gets stirred up. If so, then it will help to siphon your sandbed on a routine basis (not all at once - only a small portion at one time) and it will be beneficial to add some sand sifting critters to keep the detritus from settling back in.
Do you target feed or just dump the food into the tank? If you feed the frozen food from a feeder there is often less that gets wasted and less fodd is prevented from being able to settle into the rockwork or sandbed (a turkey baster is a simple tool for that).
Unless you get an accurate reading of your po4 then it will be hard to tell when you GFO is exhausted. Maybe someone nearby can do some testing with a photometer. Again, keep in mind that the true amount in the water column can be masked becuase algea growth can take it up before it becomes dense enough to become detectable.
Pictures will certainly help to determine if you've got cyano or diatoms or just what is growing, but the fix is all pretty much the same - manage the nutrients (the exception here is if your only dealing with an outbreak of diatoms). As spike said, diatom growth can be fueled by excess silicates which you mentioned to have high levels of.
An ATS (algea turf scrubber) is a great means of nutrient export.
Carbon source dosing (bacterial proliferation) with vodka, vinegar, sugar, vitamin C, etc....takes great care when using, but can be an effective means of removing excess nutrients in conjuction with other methods of nutrient management.
Ozone use is a very common means of breaking down organics which is thought to then make them more easily skimmed out or converted into molecules that are more easily bound to GAC or GFO.
How often do you do water changes?? How much??
How much carbon and what brand do you use?? Maybe you need to use a stronger or larger amount of carbon.
Do you grow any macroalgae?? That is an excellent means of nutrient export.
What type of skimmer?? What's the tank volume rating?
What's the tank size and total water volume??
How many fish?? How big??
Do you feed any coral food or any other addatives??
Are you using RO/DI water or something else? The most common source of silicates is in tap water or leaching from exhausted DI cartridges.
Take a turkey baster and blast at the rock a bit. Does a lot of detritus get blown off?? If so that's a good indication that flow in that area isn't sufficient enough to keep the waste particles suspended (which will eventually get them to the overflow or filter intake where it can be removed). Most of us have a few small areas where this detritus builds up, but if your finding that you can blow dust off of a lot or surfaces of the rock then you might want to consider more flow in alternating directions. Even if you've got a 10 gallon tank and a 300 gph powerhead (30X turnover) the flow will be ineffective at suspending detritus throughout the entire tank becuase it flows in one direction. More flow in multiple areas will help limit dead zones which will be helpful in preventing the decomposition of the waste that settles in those areas.
I can give you general ideas all day, but if you answer those few questions I listed, we can all help get you a more detailed plan for managing the excess nutrients.
Jeremy
