No wet/dry filters for reef aquarium?

[L S]

Hi Gregory,

Saw your para on wet/dry filter.........

"wet / dry filters are excellent methods of dealing with ammonia and nitrite in a fish only system, but are not effective at processing nitrate which can be a real detriment to reef aquarium systems."

Oh no, that's what I did precisely! I constructed a sump that is most part refugium, but has a trickle column with bio-balls in it. The refugium has a think 6" sand bed.

Could you help me understand why is it detrimental to reef aquarium?

Cheers,
L S

[gregt]

I'll try. Bear with me as I set up the background for the discussion.

The nitrogen cycle is very important to our closed systems. When the organisms in our system excrete waste, it is largely in the form of ammonia. Ammonia is highly toxic to fish and even more so to invertebrates (Hence the need to "cycle" our tanks before loading them up with stock).

Fortunately, there is a naturally occuring bacteria that feeds on ammonia and produces nitrite as a byproduct. There is a second bacteria that feeds on the nitrite and produces nitrate as a byproduct. These two types of bacteria live on the surface of just about anything in an aquarium where oxygen is also present, including the glass, rock, coral and even fish.

That's where wet / dry filters come in. They are highly aerobic areas where there is a huge surface area for bacteria to cling too. That huge surface area is what makes them so effective in fish only systems that have a large bio-load (IE: Make lot's of ammonia).

The downside to this is that they don't take care of the nitrate. In a fish system, this is not a problem, since fish can generally handle large amounts of nitrate without problems. In most cases, periodic water changes will keep the nitrate levels in check without cause for alarm.

However, many of the organisms in a reef tank, notably clams and corals, do not tolerate high nitrate levels well, and will suffer, sometimes fataly in such an environment. For this reason, we need to take the process a step further to get deal with the nitrates.

Enter the partially-anaerobic zone. In order to deal with nitrates, you need a large area that is mostly anaerobic (Has very little oxygen). This would definitely not exist in a wet / dry filter as it is a near-perfect aerobic zone. LR and LS will provide a partially-anaerobic zone deep in the heart of the rock, or in the lower layers of the sandbed. This allows them to process the nitrates.

So, will a wet / dry work if you have LR and / or LS? Not efficiently. Because the wet / dry is producing the nitrate and putting it back into the water column, it is present immediately and has to somehow find it's way to the anaerobic zone to be processed. When the conversion to nitrate occurs very close to the anaerobic zone, such as on the surface of LR, it can be processed very efficiently by the nearby anaerobic zone, before it enters the water column.

So, in conclusion. What do you do? I'd simply remove the bio-media from your filter and add more LR or LS instead.

Did that make any sense?

[L S]

Hello Greg,

Thanks for your concise explanation. After reading your mail the 2nd time, I understood it very clearly. The nitrite level in my tank is 0.1mg and seems to be improving, but I have never tested for nitrate before. That'll be on top of my to-do list.

If I could bother you with just one more question....my main tank water trickles through the bio-balls, and immediately flows thru the LR sitting on thick sand bed at a slow rate, before being returned to the main tank. Will this be considered as nitrate conversion occuring very near to an anaerobic zone?

Cheers,
longsan

[gregt]

I'm not an expert in reef chemistry, you may want to post in the Reef Chemistry forum to get a second (expert) opinion, but in my experience, with that scenario, you'll still get elevated nitrate levels in the long haul.

Keep in mind, this is not all that difficult to deal with if you are willing to do regular water changes of sufficient volume to export the nitrates. Many of us are too lazy to do so.

[CedarReefer]

What would happen if the chamber that holds the bio-balls was to be filled with water, rather then to let it trickle down through?

The reason I ask is 'cuz the area in my sump where the water from the main tank dump into was making way to much noise with bubbles. I placed the hose near the bottom and filled the chamber with bio-bail. So it breaks up the bubbles and makes it real quit while the bio-bale still remains completely submerged in water.

Sean

[gregt]

Personally, I would remove the bio-balls because you are probably reducing their efficiency too much by submerging them, and they are going to collect detrius and get pretty nasty over time creating even more problems.

I see where you are going with your thinking though, and that would be another interesting question to ask in the chemistry forum.

[quiksilver]

you could just add lots of LR directly below the bio balls and as the water filters through the bacteria it then dumps directly onto LR. Also adding a refuge after the bio balls helps. Both a refuge and bio ball sump working together have proved themselves worthy in the past. After all, the more filtration the more ballance and that is all you are really trying to establish in the first place.

Just my 2 cents.

Evan

[Mmaggicc2]

Hi,
I had the same problem with my wet-dry. I could get the nitrates down to about 25 right after a 25% water change but two days later it would be back to 50 or more. Someone at RC suggested that the problem was probably related to the fact that many people with wet/ dry filters have too much water in the sump ...partially submerging the bio- balls. I lowered the water level in the sumpso that the bio-balls are above the water line.
did smallweekly water changes and my nitrates have dropped to almost 0.
Hope this helps. Mary