Safe Zone for Nitrates in a Reef Tank
I just read an article that stated (by an apparent experienced, or perhaps even a professional) reef keeper that 0 - 20 ppm for nitrates is Ok for a reef tank.
When I converted my all fish tank to a reef tank months ago my nitrates were high - really high. I had fish and soft corals in the tank and they did fine - no deaths and apparently no stresses on anyone. I'm not so much worried about stress or death among my soft corals or fish - they seem to handle 10 ppm of nitrates easily. The soft corals are growing like weeds and spreading. Softies is all I intend to keep - no stony stuff.
My big concern is hair algae. It was the death of my first reef tank 20 years ago and I gave up in disgust and dissapointment. Now I'm trying again and all is well so far. I can keep my nitrates below 10 ppm with a 10% water change once a week. That's easy to do, it works fine, and I'm committed to doing it. Every week.
The big question is: Will 10 ppm keep the dreaded hair algae away? If I see any hair algae again, I'm running off to Tahiti to live out my life in peace.
On the flip side, you may be achieving this result due to natural denitrification within your tank. Rather than rely on water changes, perhaps you could identify more natural methods of nitrate reduction & prevention, to assist this denitrification process.
For example, do you use mechanical filtration? If so, removing all filter pads will help to eliminate unnatural sources of nitrate buildup, allowing the nitrates to naturally fall as denitrification occurs.
I am willing to bet that with a little examination of your tank we can get your nitrates to zero naturally, without all the effort. If you are interested, post some details and pictures of your setup.
In a reef, you can achieve 0ppm nitrates, which is what you want.
My reef, last time I checked, was very close to that. I'm going to be honest: I don't do waterchanges every week. I do them every 2 weeks to a month. My water quality is great, and if something goes wrong, I potentially know about it because of my Pulsing Xenia. To me, they are a water quality-watcher. They have never stopped pulsing. If the aren't, something is wrong.
The best way to achieve nitrates under 10ppm, or even 5pp, (IMO), is a quality skimmer, live rock, and plenty of water movement. Along with WC"s, of course.
Ok - let's move on. Sounds interesting.
Tank is 20 gals, ph 8.4, phosphates 0 ppm, lighting is 96 watts of T5 HO 8 hours a day. As of today nitrates were about 10 ppm. The last water change was 6 days ago, and I plan another 10 - 15% change tomorrow. I have no skimmer. The noise from the Venturi won't work in my setup because I have the tank in our family room where we watch TV and listen to stereo. Unless I can find a quiet skimmer. I'm depending on whatever water changes I need to do to keep the water quality as good as it is now.
I have 15 lbs of live rock over a bed a dead rock. I can't stuff any more live rock in the tank - if I do there won't be any room for corals.
I have mechanical filtration - an HOB filter with carbon, filter pads and a nylon bag containing Purigen to help with the nitrates. The tank is 2 1/2 months old and is doing fine. It's a conversion from a fish only tank, so there was no break-in period or new tank syndrome. I simply began adding the live rock a few lbs at a time every few days, then a soft coral once a week. The fish were already there, a clown, a wrasse and a damsel.
The tank is doing fine, and naturally I want to keep it that way. Water changes are not that big a deal for me since the tank is only 20 gals. I've kept small saltwater FO tanks for 20 years with sucess so I know what I'm doing (I think?) with small salt tanks.
This pic of my tank was taken this afternoon, when the anemone in the lower right was spread out like a corn fed pig, the Xenia in the upper left was in full bloom and the mushrooms were in full spread.
Thanks for any advice. It sure would be nice to see 0.0 ppm of nitrates for the first time in my life!!
Your aquarium is beautiful. Very nice display.
Obviously, without a protein skimmer you have a unique challenge. But knowing the downfalls of such a system allows us to take correct actions.
You are using activated carbon, which on a 20 gallon tank has the ability to nearly replace the benefits of a skimmer. It is very important that you use a high quality carbon and replace it frequently. I would personally consider a weekly replacement of the carbon, to allow it to absorb organic acids at maximum efficiency. This will help to reduce the amount of organic waste that is available to be processed biologically.
Another step will be the frequency of cleanings of your filter pad. On a system without a skimmer, I would make it a routine to give the pads a rinsing every morning and every night. Organic waste bonds with these pads, and as water flows across these organics, they break down causing an increase in nitrate and phosphate levels. By rinsing the pads 2 times per day, you will be directly removing waste before biological activity occurs.
The purigen bag is another possible source of biological activity. Have you tested the water to confirm that the Purigen is effective at reducing Nitrates? If you are not seeing a visible benefit or test results confirm this, I would remove the bag. This pouch is a source for bacteria to cling and begin biologically breaking down organic acids, depleting carbonates and producing nitrates. In a larger aquarium the benefits could outweigh the negatives, but on a 20 gallon tank without a skimmer, any artificial biological processing of waste is bad.
Fortunately for you, you have a considerable amount of live rock. This rock alone is very capable of handling all the waste load produced in your system, provided you make these small steps to help out. Keep in mind, live rock processes organic waste with an end result of nitrogen gas, which leaves the system naturally without ill effects.
Finally, ensure that you have adequate water flow across the substrate. Your larger grain size will make it easy for detritus to settle, which should be avoided. A good clean up crew will be essential.
Hopefully you have a few take aways from this. Congratulations on your success.
Pasfur - your comment about the Purigen was enlightening to say the least. I read everything I could find for days on nitrate elimination methods and settled on Purigen. No reactor is necessary and the manner in which it works was claimed by those who use it as the best nitrate reducer on the market (it duzzint really remove nitrates, it removes only the "stuff" that creates nitrates). The Purigen has been in the filter for only 10 days but I have noticed no benefit in nitrate reduction. Hmmmm. Your question "did it help?" is thought provoking, but I have to honestly answer "NO."
Okay. By day's end the filter will have only pads and activated carbon. No Purigen. After my weekly water change
Now comes a big confession of an item that I completely forgot to mention in my previous post. And it's important. After you read this, please don't send the Saltwater Reef Police after me!
In the 20 gal tank I had an undergravel filter. Never had a problem with UG's. When I strted with saltwater FO tanks, UG was the way to go. When I decided to convert to FOWLR I left the UG in place. Then, because everything was going so well, I decided to add more live rock and try some soft corals. Still, everything was great - weekly water changes kept me in business.
I know that UG filters or a "no no" in reef ranks. But it's too late now. I won't tear the tank down and start over, and I can't turn the UG off for obvious reasons.
SO - do you wanna take a crack at an option for me? Remember, it's not causing me any grief now. Should I leavet it alone, phase it out slowly (I have no idea how to do that), or WHAT? Does anyone besides me use a UG filter for a reef sucessfully? Am I a pioneer in this UG area or just someone headed for trubbell?
One last item. I have no intention of keeping any hard corals, it's softies only for me. My concern is hair algae, the scourge of every reefer.
Ok, the answer is obvious. Don't fix what isn't broken. You have a beautiful aquarium, so why go tinkering with the substrate? I would leave it alone.
However, if someone else were in your shoes, and they were experiencing the sort of problems you'd expect with an u/g filter system. i.e high phosphates, uncontrollable nitrates, alkalinity depletion, calcium depletion, and pH swings.... then I would advise this person to turn off the u/g TODAY. Just leave it in place, but stop the water flow. Then add enough live sand (well rinsed in aquarium water) on top of the existing sand to reach a total depth of 6''. A bacterial bloom may occur, followed by some cloudiness, but in the long run the tank would be better off. This is a plenum system, not to be confused with a DSB.
For the record, if you think back 15 or 20 years, when the concept of denitrification was first achieved, the idea was to convert a u/g system into a plenum system by turning off the water flow and increasing the sand depth. ;-) Today, we have now discovered that DSB systems are more effective without a plenum, and are achieved most effectively by placing the proper sand directly on the bottom of the aquarium, using 4''-6'' of sand, and lots of sifters.
LOL An u/g filter.
HEY!!! I just had to tell my wife that two people in Lex Ky are laughing at me because I'm using a UG system in my reef tank!
Remember, this was not planned. When the live rock worked so well, and I added a few corals and that seemed to be working, I kept right on going. All unplanned. Now a tear down seems like an awful idea.
This I know for fact. My nitrates are not increasing, they have been at 10 ppm for about a month now. I can only conclude that my waterchanges, live rock and Purigen are working together to kep the nitrates at a manageable level. I might try several big water changes in successive days to get the nitrates as low as I can, then see if they increase. If they don't increase, then that's a good enough reason to leave well enough alone.
I'm not averse to trying your suggestion of turning it into a backward compatible/half baked plenum system if my pioneering effort here fails me. However, if in five years my UG system has revolutionized the reef tank hobby, and the system is named after me, I will remind you that you were the one who laughed at me first!!!
Thanks for your help. You have been a big help, I have a few choices and I will keep you posted - with news both good and bad. Pictures too - both good and bad.
wait... is the U/G filter running normal or reverse?
Normal. Down through the grate and up to a power head and across the top of the water.
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