RC, is it the wet/dry part that causes nitrates?
Okay, in simple redneck terms. Somebody might want to argue specifics or even semantics - but I'm going to post MY understanding of the nitrogen cycle. If anybody has a different way to describe it - fine by me. This is MY particular understanding of how it works.
(ya practically gotta be a lawyer before you can even think about discussing anything technical around some of the users on this forum :grumble: )
Nitrates are a natural part of the nitrogen cycle. Any time aerobic bacteria break down the waste in our tanks it going to contribute to nitrates. Live rock causes nitrates :shock: - yup. And it also breaks those nitrates down. Wet/dry filters cause nitrates too. It's a natural part of the nitrogen cycle. So do canister filters. And undergravel filters. And reverse movement fluidized sand beds. And HOB filters like those Whisper bio-wheel things or Penguin whatever things - HOB filters with cartridges that slip in and out.
Nitrates are a part of the cycle. Unfortunately, they are an unwelcome part of that cycle. So the challenge to the reefer is how to get rid of the nitrates. First you need to know a little about the bacteria that cause these nitrates. These are the kind of bacteria that live where there is plenty of oxygen. They are called aerobic bacteria. A generic term for any bacteria that lives in an oxygen rich environment.
Aerobic bacteria break down the more complicated ammonia compounds like fish pee, uneaten food etc... That ammonia gets broken down into nitrites and then those nitrites get broken down into nitrates. All this conversion is performed by aerobic bacteria. They colonize on the surface of almost everything in your tank. They grow on the sand grains, the pipes, the rocks, even the shells of the snails and crabs. They are mircoscopic bacteria that absorb and digest these compounds from the water. If there is oxygen - they are there - doing their job to break down the most toxic compounds in your tank - but at the same time they leave behind nitrates. Thats when these little bacteria stop. They don't have the ability to absorb and metabolize the nitrate compounds. So the nitrates build up in the tank unless they are removed by water changes or filtration.
For breakdown of nitrates, you need anaerobic bacteria. These bacteria live in an oxygen depleted environment. They live deep down in the sand bed where there is significantly less oxygen or sometimes even no oxygen at all. They live deep inside the live rocks in your tank, where water circulation might be 1x turnover per DAY. These anaerobic bacteria can break down the nitrates. The end result is harmless nitrogen gas. The nitrogen gas bubbles out of the sand bed and gasses off at the water surface because of water movement generated by powerheads or filters.
What does a DSB do to the water quality is it something in the sand like a bacteria?
The DSB is where the anaerobic bacteria live. It needs to be at least 4" deep. 6" deep is better and 8" is even better. The AEROBIC bacteria live in the top 1" -- 2" of sand where there is plenty of oxygen. This is also where many of your pods
(copepods) live. The reason a DSB works is because most of the oxygen is used up by the surface inhabitants. By the time you get down 3 or 4 inches into the bed - oxygen levels are reduced enough that your ANAEROBIC bacteria will begin to grow. Even though the water is fluid and moving through the sand bed, most of the oxygen still gets used up long before it can penetrate into the lower regions of the sand bed. The nitrates are still there though. When the water moves all the way down to the lower regions of the DSB the anaerobic bacteria will feed off the nitrates and break it down. The resulting gas is harmless nitrogen. It works it's way up through the sand bed and off-gasses at the surface of the water.
My LFS guy is in love with the wet/dry thing and swears that they work as long as the water "trickles" over the balls and is not submerged.
You need to keep detritus and debris off the bio balls. That means washing them frequently to remove stuck on goop and rotten organic materials. Most people wash the balls in salt water that was removed from the tank during a water change. The reason bio-balls get blamed for nitrates is because they DO produce nitrates.. It's the natural breakdown of the chemicals. Bio-balls and any other filter that relies on oxygen is going to produce nitrates. PERIOD. It's how you the reefer handles those nitrates. Do you remove them via water changes? Or do you build a nitrate reactor and use a mechanical device to remove/reduce them? Or do you let nature do the work for you
(my preferred method) and use a DSB?
Many bio-balls get no maintenance at all. They are left to collect and trap rotten food, fish poop, etc.. for months or even years at a time. This will certainly contribute even more to the nitrate problem because the trapped debris is left to rot and dissolve into the water. These solids should not be left to rot. They should be removed from the water either by your CUC, mechanical filtration or some other method. Poor tank husbandry leads to nitrates. But you can't blame poor tank husbandry on ALL nitrates. Don't forget that nitrates are a natural step in the overall nitrogen cycle. They will get produced and you will have to deal with them. Again it's how you deal with them. Be it natural, mechanical, water changes or perhaps some other way.
Another person told me the only true way to clean water is the way nature does it, by putting it under a UV light. What about adding phytoplankton?
I can't comment. Never used one.
Ugh, this is confusing.
C
Hope this helps.
