Nitrates keep goin up

[joejoe]

Hey all a week ago my nitrates were at around 90, so I took some advice and did 2 15 gallon water changes on my 38 gallon tank. The nitrates dipped back down to 25ish on Tuesday, but when I just checked them they were at around 50. What gives?? I know I'm not overfeeding and I cleaned my sand bed and all.

 

[clown_nut]

well what all is in your tank and what kind of cleanup crew do you have? Also if you have a bio-wheel i've heard some here say that those things are nitrate factories.

 

[greatfullreefer]

You say you clean your sandbed. This may be a bad idea, whilst stirring and cleaning it you may be releasing the nitrates and other polutants. Get some sand shifters to keep your sand bed clean.

 

[joejoe]

Nope I don't have a biowheel. I was thinking that cleaning the sandbed might in fact have released some nitrates into the water. If I continue with what I'm doing, will the nitrates go down over time or would another 15 gallon water change be a good idea over the next couple of days?? As a cleanup crew, I have 2 turbos, 15-20 nassarius snails, 2 cerith snails, and around 10 blue legs. The other livestock includes 2 cleaner and 2 peppermint shrimp. What do yall think??

 

[sly]

Sounds like a good clean up crew.
There are two basic ways of having a sand bed, deep and shallow. If you have a deep sand bed then that means that you will have some low oxygen areas within the sand that will house bacteria that eat up nitrate. The sand bed can't be too deep or you will have areas that are totally oxygen free and you will get hydrogen sulfide instead and poison your tank. Anyway, if you stir the deep sand bed you will disrupt the bacteria living in the low oxygen areas and kill off some of the colony leaving nitrates with nothing to eat them. Also you release gunk that was in your sand bed into the water which also has nitrates in it. All you need to do is lightly vacuum a DSB to keep the crud off the top but don't stir it.
The other method is to have a shallow sand bed that's about 1 inch deep. This bed will have high oxygen levels throughout and therefore not house the bacteria that eats nitrate. Instead you can use lots of living rock to house the bacteria and plant macro algae that will absorb nitrate as well. Stir a shallow sand bed frequently to keep it clean. Keep it mixed up and clean. You will not release nitrates because it it too shallow to house the bacteria anyway.
Make sure all of your filter floss and sponges are kept clean and don't have nitrate adding build up on them. Also add some carbon to the filter to help absorb junk.
If you have a DSB then you should probably do another water change but don't stir the bed. Let it sit for awhile until your bacteria are built back up and your nitrates start going down (or at least stop going up). Then do a final water change once your DSB cycles to remove the excess nitrate and your done. :happyfish

 

[joejoe]

Awesome thanks Sly!! My sand bed is around 3" deep so I'm gonna go ahead and start prepping some salt water for another partial change. Thanks!!

 

[dreeves]

Doing water changes will only dilute the nitrates...nitrates are created as a process in the nitrogen cycle...they accumulate in most tanks due to the lack of water changes, and/or nothing to naturally remove them...be it macro algaes or the DSB.
You need to address the issue of where the nitrates are coming from before you can maintain a control on them...you will always have certain levels whether you see it or not with a test kit as it is a natural occurance...our goal is to keep them controlled naturally.

 

[sly]

I think we've already addressed the issue in that he just stirred his DSB for the first time and then suddenly his nitrates started going up.

 

[dreeves]

Try not to think too hard...
Stirring the sandbed after it has already been up is hardly the cause for the high nitrates to begin with...

 

[sly]

You're right. But Nitrates accumulate naturally as a result of the nitrogen cycle and stirring the DSB will distrupt the nitrate absorption of the cycle resulting in climbing nitrate levels.
Also over time DSB's become saturated with wastes in the anaerobic areas of the substrate and stirring them will release toxins in the tank which then break down further in the higher oxygenated areas of the tank, releasing more nitrates.
His nitrates were high to begin with, probably due to poor maintainance. Suddenly he did a water change and also stirred his substrate, i.e. destroyed his biological filtration. Now the levels keep climbing but have nothing to absorb them.
He needs to make sure his mechanical filters are kept clean on a regular maintainance schedule and needs to do periodic water changes without greatly disturbing the substrate.
Other than dirty filters, the source of nitrates could be that there are too many fish in the tank or something has died.

 

[thedraven]

Sly, how deep should an average dsb be? My current sandbed in my 75 is three inches deep and my nitrates have never risen above 15ppm. Would 4 inches be better for my new tank?

 

[sly]

The only real scientific way to know how deep to make your DSB is to physically measure the ammount of oxygen in the bottom layers of the bed.
If you have no dissolved oxygen at the bottom of the bed, then your DSB is too deep. You also don't want too much oxygen in the bottom layers, meaning that your sand bed is too shallow. It also depends on how much water movement you have at the surface. The more water flow you have, the more oxygen will get to the sand, and therefore the deeper it will have to be to keep sufficient oxygen poor areas.
My personal belief (take it with a grain of salt) is that 4 inches would be better. But I don't know how to tell you for sure. There are just too many variables.
Maybe someone else can simplify it...:notsure: