Nitrate Concern- Discussion for long term fix

[firsttank]

Tank Details:

Started october 2009- 65g tank , Reef Octopus DNW150 , 15g bare bottom frag tank , 30g mud sand bed refugium , Mixed Reef , T5 lighting,

Fish: 3 wrasses, 1 yellow tang , 2 clowns, 1 fire fish

Feeding: Fish get fed 3 times a week with Rods food.

History:

I upgraded my refugium from 15g to 30g in July 2010 and during this process I decided to go bare bottom on the refugium with just rocks and calupra.

Slowly detrius started to build up in my frag tank and refugium and my nitrate were increasing and it hit about 100ppm ( salifert). With it cyno started to show up as well. Before July 2010 my nitrates read "0" ppm.
Phosphates are at 0.04-0.06ppm ( Hanna)

To fix the problem I decided to put a sand bed in the frag tank and refugium to allow the bacteria to colonize and help break down nitrates.

Also as a temp fix I started bacteria dosing with vodka for 1.5 months. This helped me to bring it down to 40-50 ppm . I eventually want to get rid of bacteria dosing completely as I travel and it will be hard to maintain the routine. I was hoping that as I dose bacteria the new sand beds would seed fast but I am not seeing that effect yet.

Questions:

How long does it take a sand bed to colonize and start breaking down waste effectively?

Do I have to always continue to dose bacteria and vodka to keep the nitrates down ?

Do I have to go the route of Denitrator? , if so do I go with the media reactor or the coil tube reactor?

Bottom line: I am looking for a long term solution Plz help me get to a decision.

 

[DustinB]

Can't comment on the sandbed for certain, but even on a new tank with live rock to seed the sand, I noticed my sandbed was active with life within 2 months.

If you dose carbon you will need to continue, but with your bioload a maintenance dose should be rather small, as in @1ml of 80 proof vodka. You can buy a dosing pump pretty cheap and a small bottle of vodka. Your dosing pump should run for almost a year before you need a new bottle. This would be your cheapest and maybe easiest option if you can't get a refugium to keep everything at 0.

Right now I'm dosing 1.15ml 80 proof vodka equivalent on my 90g w/20g sump as a maintenance dose. It's actually a solution of vodka and vinegar at .75ml 80 proof vodka with 2ml distilled white vinegar. No refugium anymore, no GFO anymore.

Which option to go with is really up to you. I have seen people run huge refugiums and have no nutrients. Same goes with sulfer reactors and carbon dosing. Carbon was the most appealing method to me given the cost and the ease.

 

[Amphiprionocellaris]

Hey there!

This is actually my field of expertise, so I hope you can forgive a long and semi-technical answer...I hope it's more illuminating than confusing!

First of all let me say that I ran some quick numbers, and with nitrates in the 40-50 range, you're actually phosphate limited - instead of/in addition to carbon - in terms of metabolizing nitrate out of the system (as a quick review if anyone isn't familiar with it, the idea behind the vodka method is that many aquaria are carbon limited, because every ppm nitrate metabolized requires about 100 ppm dissolved carbon, based on the Redfield ration of C:N = 106:16:1...aquaria typically have way more nitrates than in nature, hence the possibility of being limited by carbon). In your situation, a nitrate level of ~40 ppm would correspond to a phosphate level of ~2.5 ppm. Granted, that's just a generalized figure, but the point is that, even with completely effective carbon dosing, you're still only going to pull nitrates down by about a pretty small amount using just that.

What that ratio doesn't take into account is anaerobic bacterial metabolism, which is going to reduce nitrate to free nitrogen gas (without regard to phosphate concentration), so as your sand bed really gets cranking, you're going to see a pretty dramatic drop in nitrates assuming it's deep enough to allow anoxic conditions to develop. It's important to note, however, that this drop is going to be limited by the speed of diffusion of nitrate from the water into anoxic areas of the sediment; nothing we can do will make that go faster. It's also important to keep in mind that this system will take time to establish an equilibrium and balance metabolic rates so that you have a net consumption of nitrates. This equilibrium does, though, require a lack of disturbance, and to see a net drop in nitrates also requires that the rate of nitrate production (from feeding, organics added to the tank, etc) be less than the rate of denitrification.

Now where I'm going with this: by dosing bacteria, you're continually adding new biomass to the system, some of which is certainly going to die off and decompose. So, although you may have a very active sand bed, you're not seeing the effects because so much fresh material is being added. Getting rid of bacterial dosing is not only going to be easier on you, but it will allow the nitrates to really come down all the way; it may be counter-intuitive, but more bacteria added may actually lower the efficiency of denitrification! That phenomenon is actually really complicated; I would be more than happy to explain it if anyone is interested, but I think I've already used enough space

Hope this helps and wasn't overly complex!

~A. ocellaris

 

[Fishtastic]

right now bacteria, nuff said. (yes, flame away those who haven't tried it)

 

[ruprecht]

...mud sand bed...

There is a chance that if the majority of sediment is anaerobic the denitrificating bacteria may actually be making ammonia thus feeding back into the system more nitrate. An efficient and healthy sand bed is a balance between grain size, surface flow, infauna, nutrient load, and overall design. Just putting one in may not be enough to solve your tanks needs as water changes can go a long way to maintain lower nitrate values.