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Nitrates


ajonesphoto

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ajonesphoto

My nitrates are between 20-40, they were up over 100 and I did two 40% water changes in a week and got them down to 20 and now I've just been doing 20% water changes twice a week but they won't budge. I've got a couple mushrooms, a couple trees, two clown fish and a yellow wrasse in a 20 gallon tank. What should I do?

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It's all about nutrient export. Water changes are good, so that's a good start. Are you skimming? Do you have a lot of detritus build up? Before you do a water change, try taking a turkey baster and stirring up any detritus by blasting your rocks, and then siphoning out as much as you can. You might also try Dr. Tim's Waste-away to help remove sludge.

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+1 to nutrient export. You have a relatively high bio-load in the tank. Now much do you feed? If feeding frozen do you rinse it?

 

Having a nitrate issue isn't super difficult to solve, but it does come down to nutrient export. The final step to get rid of nitrates I believe has to do with nitrogen fixation - which is usually done by the anaerobic bacteria in your tank. These are the bacteria present in deep sand beds or deep within rocks where no oxygen is present. The other way to reduce nitrates is through the rearing of organisms that absorb it such as algaes, plants, and some soft corals and such. Skimming and other chemical reactors can also help a lot.

 

As to your nitrates - they seem extremely high... Anything over 30-40 usually causes major issues. Are your test kits expired ? 100 seems, well, insanely high.

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Nano sapiens

The short answer is start to remove built up detritus one section at a time (not all at once).

 

A clogged substrate makes it difficult for the bacteria to function properly. This, and the break down of detrital organic matter, contributes to nitrate and phosphate issues.

 

Denitrification occurs efficiently in shallow substrates due to an effect termed 'coupling'. Micro pores in the sediment harbor anaerobic denitrifying bacteria in close proximity to aerobic nitrifying bacteria and this close associatiion leads to efficient nitrification and denitrification. But only if the substrate is relatively clean.

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A clogged substrate makes it difficult for the bacteria to function properly. Micro pores in the sediment harbor anaerobic denitrifying bacteria in close proximity to aerobic nitrifying bacteria and this close associatiion leads to efficient nitrification and denitrification. But only if the substrate is relatively clean.

This is why I might actually get a few scarlet hermits. I prefer going clawless, but I haven't been extremely happy with the performance.

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ajonesphoto

What do you mean by detritus? My sand is clean, every time I do a water change I stir up the sand with the siphon. I do have some green and red fuzzy looking carpet algae on my live rock. When I got the 100 result I was using an api test kit but now I use the Red Sea kit. I don't have a skimmer, when I went to the reef store to establish my tank they said all I needed was a filter with three levels of filtering and a water flow machine. They never talked to me about a skimmer.

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Nano sapiens

What do you mean by detritus? My sand is clean, every time I do a water change I stir up the sand with the siphon. I do have some green and red fuzzy looking carpet algae on my live rock. When I got the 100 result I was using an api test kit but now I use the Red Sea kit. I don't have a skimmer, when I went to the reef store to establish my tank they said all I needed was a filter with three levels of filtering and a water flow machine. They never talked to me about a skimmer.

 

That's a good start to a clean substrate. However, that's just part of the nutrient build up process.

 

Have you ever vacuumed under your base live rock? If not, you'll be amazed at what the advection process deposits under our reef structures. This stuff leaks out over time into the water column which causes steadily rising NO3 and PO4 levels.

 

If you don't want to disturb your rock work, then you'll be dealing with the NO3 and PO4 after it enters the water column, via water changes, GAC and likely GFO. Lots of people do this, but some (like myself) prefer to go after the root cause before it has a chance to pollute the system. I can keep 10g of water (with a good sized bio-load) at untestable NO3 and PO4 all day long (years long, actually) as long as I have a good maintenance plan and routine.

 

Skimmers are an aid to help remove organics from the tank, but are not a necessity for a healthy and clean tank. In smaller nano tanks that have frequesnt water changes, they are just not worth the extra hastle, IMO.

 

A mechanical filter can help somewhat in sequestering water borne particles (detritus, food, etc.), but the medium (floss, usually) needs to be cleaning or replaced frequently to limit decomposition in the system.

 

As you can see, how one go about nitrate reduction is a personal choice, but a continuously fed system with insufficient export of nutrients will have ever increasing levels of NO3, PO4 (and other noxious compounds).

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Detritus, as it relates to a reef aquarium, is all the dead organic particles in the tank. Things like uneaten food, solid fish waste, dead plant or algae matter, etc... Some tanks experience a lot, others don't. Usually though, it accumulates over time as a tank matures.

 

Good post sapiens. Your last sentance pretty much sums it all up. Whether you remove detritus in particle form or later on as dissolved organic compounds nutrient export has to be dealt with at some point.

 

I can attest to the accumulation of detritus though. In my new tank that's only a few months old it's not much of a problem, but in my older tanks I was able to extract quite a bit on cleaning days. It usually settles on/in the sand and on/in rocks. To keep the time I spend sucking it out to a minimum I maintained a lot of flow in the tank and I used a turkey baster to frequently "blow off" rocks. The combination of flow and using the turkey baster gets the finer detritus into the water column so it gets traped by the mechanical filtration - then I just clean/replace that frequently.

 

Skimmers and chemical media reactors aren't always necessary, but it depends on the tank. If you have a lot of fish and you feed heavy or slack on water changes you need more filtration so a skimmer is going to be more necessary. If you understock or do regular water changes you probably don't need a skimmer. Normally I don't recommend trying to cut back on feeding too much to solve a nitrate problem unless your existing regimen is way too heavy.

 

Another idea is to increase the # of detrivores in your tank (organisms that consume detritus). Good detrivores are things like hermit crabs, sand sifting snails like nassarius, and a healthy population of pods and worms is also pretty effective though that will be difficult in your tank with the wrasse since it hunts them. Encouraging a healthy population of detrivores can help a lot.

 

Here's a cool read: http://www.reefkeeping.com/issues/2002-03/rs/

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ajonesphoto

I have a hermit crab and a snail, I don't usually blast my rocks so I will try that. I only have 3 small fish in a 20 gallon tank, I use pellets not frozen food right now, I just use a tiny pinch for all three fish. I also have a couple of peppermint shrimp who tend to clean off the sand so I don't know how detritus could be a problem in my tank, not all my rocks are glued down and so cleaning under the rock would be difficult but I do weekly 20% water changes. After my two 40% water changes I noticed my mushrooms and trees were considerably healthier, my fish also seem more active but it just seems stuck between 20-40(nitrate level).

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Peppermint shrimp won't be able to dig into your sand and clean out anything but the top layer (if you've got oolitic sand you wouldn't need to worry about lower layers, I suppose). Plus, they're scavengers, not detrivores. What they're picking up is leftover food.

 

Do you have sand sifters? How often do you replace your mechanical filtration?

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SchnauzerFace

I have a hermit crab and a snail, I don't usually blast my rocks so I will try that. I only have 3 small fish in a 20 gallon tank,

 

One snail and one hermit crab won't be able to keep up with 3 fish. I suggest increasing your CUC. Snails that burrow into the sandbed (nassarius, for example) are very good choices. I don't like crabs, but I have to admit they do a good job of keeping things tidy. Detritus collects faster than you may initially realize. A fish tank is basically just a giant toilet bowl.

 

What are you using for your three stages of filtration? If you're using a sponge or filter floss, are you cleaning and/or replacing it often? I don't know what you've got at the moment, but filter floss + chemipure elite + purigen is a good starting point for a tank of your size.

 

I don't think that a skimmer is 100% necessary for a 20g tank, but 2 clowns and a wrasse is actually a decent sized bioload in a 20g. You might want to consider a skimmer. Of course, you can still manage your parameters with frequent water changes, a bigger CUC and careful attention to any sponges or floss that could collect detritus. The suggestion to blow the junk off your rocks is also a fantastic starting point.

 

Just to make sure -- you're using RODI water to mix your saltwater, right? Or are you just buying premixed stuff from the fish store?

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ajonesphoto

My filter has a sponge, then black carbon and then a rock type stuff layer. I change and clean regularly. I have a water softener and reverse os osis system built into my tap.

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I'd replace the sponge with filter floss, something you can buy in bulk, cut down to size, and replace every day or two. Make sure your carbon is still active, because once it's adsorbed what it's going to adsorb it's done, no more filtering. What's the rock type stuff? If it's biological media, you want to check that it isn't accumulating detritus and therefore just building up nitrates.

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Definitely increase your CUC. Reefcleaners.org look at quick crew packages and check out the numbers for the 20L. That's what you need.

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