[wozza]

Hi I have a 120lt with:

6kg live rock
1, 4 inch lion
1, 3 inch clown
1, 3 inch royal gramma
misc inverts

if I was to attach a 15lt refugium would this actually help in reducing my nitrates in any significant way?
Cheers James

[tray262]

Can you add some more info. Like what kinda of filters you are using, you may want to looking into a deep sand bed aka DSB. The refug would be more of a place to house macros and grow some pods.

[Ninong]

A refugium is supposed to be a "safe place" free from predation. It's from the Latin fugere (to flee) and when you add the prefix re-, it means to flee back to. Adding the -ium suffix makes it a place. So it's a place to flee back to or a safe place of shelter.

However, it has lately taken on a new meaning the hobby as a supplemental filtration method using a deep sand bed for additional denitrification. Whether it would make much difference if you add a 4-gallon (15l) refugium to your tank is questionable. It certainly wouldn't hurt but it wouldn't be as effective as simply adding more live rock to your main tank. You could increase your live rock from 12kg to say 15-20kg.

Do you have a sandbed in your main tank? The sandbed in the main tank itself is more effective (much more effective) than a tiny sandbed in a separate 4-gal refugium. However, if you put some Chaetomorpha or similar macroalgae in the refugium and harvest periodically, that will export nutrients and be a help. Macroalgae in a refugium would be more in line with the original concept of what a refugium is supposed to be and if you harvest it on a regular basis, you are exporting nutrients. It could also be a good place to harbor amphipods and copepods where they would be free from predation and allowed to multiply. In which case, you would want a little live rock rubble in there.

The bottom line is that a refugium always helps but if your goal is to increase denitrification, adding more live rock to your main tank would be more effective than a 4-gal refugium.

P.S. -- Aren't you afraid that the lion might eventually eat the clown and the royal gramma?

[wozza]

Ok currently for filtration I am using:
6kgs of live rock
a fluval biolife internal wet/dry
a fluval 2+
a fluval 3+ with poly filter instead of the foam

My aim is to get rid of all the internal filters and lower my nitrates

I have a sand bed in my main tank that varies between 1 inch to 3 inch.
Also I have read that it’s not recommended to have a DSB in your main tank.
I think it was because you should not disturb the sand bed because if the anaerobic bacteria get to much oxygen they start to produce a toxic compound I cant remember the name of!!
Is there any truth in this??


Ok ill go about buying some more live rock as well.
You reckon I can go up to about 20kg?
Then just have power heads moving water over them?

And I could add a refugium to aid with denitrification.
Cheers James

P.S. -- Yeah I am when it gets bigger, but when he gets to a size that he may be able to eat them, im either going to have to sell the poor little sod or get him a bigger tank but for now he is being well fed and im keeping an eye on him.

cheers james

[Ninong]

I wouldn't put any more than 20kg live rock in your size tank but that's more a matter of personal preference. Just add another 5kg and take it up to 17kg. That would help. Then if you want more, add more later on.

Your understanding of deep sand beds is incorrect but that's a very, very involved topic. Let's just say that I recently took down my 120-gal tank exactly three years after starting it up and the 6" DSB was functioning perfectly all along. The guy who purchased my live rock and live sand was surprised that there was no bad odor at all when he removed the DSB. None! Even when he got down to the very bottom of the tank. It was a very active, very alive deep sand bed.

[wozza]

my dad is a chemist i was also worked in a chemistry lab for 4 years so i have an ok understanding of chemistry, but by no means degree level but im sure my dad would explain.

so if you feel inclined you could try to say why it is incorrect? but no worrys if you cant.

thanks james

[Ninong]

James,

There is no corrrect single answer to how deep a DSB needs to be to provide denitrification. A 4" DSB will be more efficient than a 2" sandbed but the 2" sandbed will still provide significant denitrification.

One author may write that it needs to be at least 6" deep, another may say it needs to be at least 4" deep and another may say it needs to be at least 3" deep. All are correct for what they want their DSB to accomplish. Still, a sandbed that is 1.5"-2" deep is better than no sandbed at all.

The main thing you want to avoid is using crushed coral for the substrate unless you make it very shallow (~1cm) and clean it often. A crushed coral substrate will trap detritus. A DSB of fine particle sand will process detritus and should never be disturbed.

You might check out Dr. Ron Shimek's articles on sand beds and Dr. Rob Toonen's sandbed articles. Toonen's article Part I and Part II. Shimek's sand bed articles are on this list on his website -- just keep scrolling down until you get to Sand Beds. He links six articles there.

Here is Rob Toonen's website in case you want to read some of his other publications.

P.S. -- I might as well link Jonathan Lowrie's DSB recommendations, too. This was written eight years ago. Notice that he recommends a minimum of 6" deep but says that 8"-10" would be better. He's trying to get the sandbed deep enough for all the various cycles to take place.

P.P.S. -- And Morgan Lidster at Inland Aquatics runs deep sandbeds that are much deeper than any of the other guys. Some of his DSBs are 12"-18" and his composition is different than what most others recommend. I'm just throwing this on here for the sake of diversity.

[wozza]

exelent thanks ninong, as allways you have been a great help