How long until I see the benefit?

capt. insano

New member
I have begun growing Macros in my sump to help bring down the nitrates in the tank. The tank is a 240 G FOWLR, with some pretty big "mess makers" (aka the 7 inch puffer and the trigger)

I have Gracilaria Salicornia, Red Grape Caulerpa (?), Halimeda, and several sea grasses that are starting to grow off of some live rock that I put in the sump. These algae are growing at an astonishing rate....surprisingly, even the Halimeda (I have read that these are a slow grower, but mine has produced several new, inch long arms in only a couple of weeks)

The nitrates have not budged...from their current level of 30 ppm How long until I see them going down? I have a pretty awesome protein skimmer on the tank, which I have to empty once a week. I have also dramatically decreased feedings. Thanks for you help
It takes a LOT of algae. How big is your sump, and how much algae. On a 240 gallon aquarium I would say that you would have to have something the size of a 20 gallon tank completely full with algae before you will notice much and when I say completely full I don't mean just coviering the bottom. I mean from top to bottom so you need something even bigger to allow for growth. One of 55 gallon aquarium's sole filtration is a 10 gallon aquarium that is completely filled with Caulerpa.

Also you say that you only have to clean your skimmer once a week. Skimmers, no-matter how good, should be changed as frequently as possibly. Clean skimmers work more efficiently.

Also, do you do water-changes? But really if you are not having algae problems, 30 ppm is not bad in a fish only tank, as NO3 is non-toxic.
The sump is about 40 gallons, and while it is not completely full, I am constantly adding more varieties of Macro algae. I have also begun to grow some Halimeda and spaghetti aglae in the main tank, with success.

I am going to plumb in a 150 gallon additional sump, with a 6" you guys think that this will help in my quest to lower the nitrates. My nitrates are higher than 30 ppm....they are about 80 (mis-quote on my part)

I only feed every other day now, and I do completely cleanse the waste recepticle when I empty the skimmer (life-reef skimmer)
At 80 ppm, a new filter alone just isnââ"šÂ¬Ã¢"žÂ¢t going to cut it. The only solution is to do some major water changes.

Yes a DSB will remove nitrates and the extra water you would be adding would also help a lot. But it is going to take a long time. A DSB must first cycle before it starts helping anything. First the sand must be colonized by aerobic bacteria that must prosper so well that they use up all of the oxygen in water the sand bed. Then anaerobic bacteria recolonize the sand after all of the aerobic bacteria suffocate. This takes time. But even once it is going the process is slow at removing nitrates, because the design requires that very little water flow between the sand and the aquarium to keep the oxygen level low. There is probably less than 1 gallon of water that would be filtered by the DSB per day. It would take more than a year for it to bring your nitrates down.

If your nitrates are that high, it is likely that your phosphates are high as well. First more complex plants and macro-algae can not compete with simple microscopic algae when nutrients are high, but thrive when nutrients are low. You will find that slime algae will smother the macro algae. If that doesnââ"šÂ¬Ã¢"žÂ¢t kill the algae it will slow the growth significantly.

Though neither of these options will bring your nitrates down, they are great at keeping them low once you get it down. What you need to do is start doing some major water changes, 50% or more. After 3 of them your nitrates will be down to around 10 or so, then algae or DSB will be able to stabilize it. I understand that a 50% water change is a LOT of work on a large tank but it is the only way you are going to get those nitrates down.


Thanks for the reply Acro,

We actually do 25-30% water changes every 3 weeks, and always have for the last 2 years. The water changes are done with RO water.

In conjunction with plumbing in a 150 gallon sump with the 6" DSB, I am also considering slowly removing the bio-balls from the Wet/dry (after reading so many articles debating this) What is your opinions on this?

I do have about 90 lbs of LR in the tank, and will be adding about 50 more over the next month.

I empty the skimmer collection cup (life reef) about every 5 days.

I have cut feeding down drastically in the last few months, but still those darn nitrates hang up there.

What else could I be overlooking or not doing?

I utilize a canister filter every so often, filled with Activated carbon to "polish off" the water....only running it for a day or two, then shutting it down again. The substrate in the tank is about 3 inches deep (crushed coral)