Backyard Aquaponics
A place to discuss aquaponics

Hi all,

I am new to aquaponics and this forum. I have had my system up and running for approx. 30 days.

I was hoping somebody could help me with a question regarding nitrates. My ammonia and nitrite levels are very low, but the nitrates are very high.

My question(s) Is this normal for a new system and what do I need to do to rectify it?

Thanks for any input.

Keith

it's normal.. get your plants in to start using up the nitrates

Thanks very much. I've had the 1st grow bed planted for nearly 30 days. From what I've read I need more grow bed area given my fish tank size (approx 140 gal w/ 42 tilapia) so I added the second grow bed last week and scrambled to get it planted.

http://www.backyardaquaponics.com/forum/viewtopic.php?f=45&t=11003

ammonia .25 nitrite .25 nitrate 100+

Do you think this is safe to wait on the grow beds to catch up and do you think I have enough grow bed area?


Thanks again.

This is from a fellow newbie. If you search this forum for "ratio", the first result says the following (which I've heard many other places here):



**Please double check my math**

In standard that's 2.25 lbs of fully grown out fish to 25 gallons of grow bed. Assuming that you harvest your fish at ~1.125 lbs (for easy math), that's 2 fish for every 25 gallons of grow bed. I'm guessing you have ~300 gallons of grow bed, so you would want ~24 fish. At this level of stocking... when your fish are all grown up, you still have enough filtration for all of them. I have 500 gal of grow bed and I have 45 fish (granted, it's only 2 weeks old, so take this with a grain of salt).

As for your nitrate problem... if your system is cycled and your have more fish than your plants can handle you're going to have high nitrates. Even if you have small Tilapia, one of your grow bed has half grown plants and your member page shows the other has no plants (don't know if that's up to date). So... you could buy some plants from a nursery that have already been started and work them into the bare grow bed (or add another), or maybe fill a wading pool with your AP water (replacing it with fresh water) and grow some duckweed. The water change would reduce the trate level in your system and the duckweed would eat all the nitrates, cleaning the water. Good luck!

Thanks for the info. I guess I am way short on grow bed space or have way too many fish. I have 130 gallons of bed space with 1 more to add @ approx 60 gallons. I read somewhere a 1 fish to 5 gallons of water ratio and a grow bed to water volume ratio of 2:1 so I was looking for 20 - 25 fish. (100 gallons of water, 20 fish 200 gallons of grow bed space). I had a difficult time finding the fish. When I finally did, I ended up with 43 of various sizes and figured several of them would die. That did not turn out to be the case - only 1 died.....so far.

Thanks for the suggestion on the duckweed. I will look into that as I really don't want to sacrifice any of the fish and doubling my grow bed area is not really an option.

Thanks again.

Another thing... I think if you cut the feed way back, the fish will produce less ammonia, which will in turn mean less nitrates. Of course your fish will never get any bigger that way, but it may be a way to not kill all your fish in the meantime.

You could also consider draining some water. That will help reduce nitrates to a 'comfortable' level for the fish

If you're growing out your fish, this might be a good way to feed them for growth and keep the environment clean. When they're adults, you can feed them less and create a balance.

Even if the plants eat up the nitrates, it will never remove all contaminants. A regular water change is always healthy (think heavy metal concentrations for one --- the more water evaporates, the higher the concentration goes up unless there is something to remove it --- this can be from it being absorbed in plants, fish, or by water changes).

Is this something you've experienced or heard? I don't remember reading anyone here who does regular water changes. What would be the source of these heavy metals entering the system? Sorry, off topic for the thread I suppose.

Found an interesting link below stating that "nitrate is not toxic to Tilapia whatsoever", with a reference. Obviously too much of anything isn't good though.

http://diyaquaponics.com/forum/viewtopi ... 5&start=20

Thanks for all of the helpful information.

I think I am going change a bit of the water as a temporary measure until I get additional grow bed space up and running. The second bed is 70% planted. I will pick up a few plants that I can transplant to help.

I have too many fish but am going to try keeping as many as I can (I have 2 that are ready for the dinner table now and two others not to far behind that. I'm just gonna have to eat them sooner than I was hoping).

I will also cut back on the feeding for a couple of weeks.

Thanks again.

Some heavy metals such as lead, zinc and copper may leach from old pipes or galvanized or copper water pipes. Heavy metals may also be present in certain types of rock, substrate, etc. Outside soil is full of the stuff and from industrial processes, it gets aerosolized.

Also, take a look at your local water report.

The link for Salinas, California...
http://www.calwater.com/wq/contaminants.php

So that's not a lot of stuff... water evaporates, metal stays behind, refill, evaporate, refill, evaporate... concentration increases.

It's healthy to do WC, don't fight it.

Being a veteran of internet forums and BBSes before that, I know how these things go. People latch on and get on their soap box and from the link you selected, I'm getting the impression someone might go there.

So let me set the record straight... I'm not saying do a WC b/c it's "do or die". I'm saying, it doesn't hurt and it will most likely help. The heavy metal concentrations are extremely low and even after several evaporation cycles, you're probably still safe. Now, your surrounding environment, atmosphere, fish feed and other factors may increase the heavy metals, but generally I would say it's not a huge concern.

With that said, there are other things in water that are unhealthy...

Also keep in mind, my recommendation is associated with bioload. A high nitrate reading is indicative of a higher bioload than the plants/system can handle. If that's the case, a WC is helpful. In fact, I think one of the Backyard Aquaponics articles actually recommends WC for these situations.

Here's one that says changing water reduces mortality in shrimp farms.
http://onlinelibrary.wiley.com/doi/10.1 ... x/abstract

Conclusion basically states it is due to high bioload. I almost feel that sometimes people forget there are fish in the aquaponics system and that they are going to eat these fish. Poor water quality increases disease and stresses fish out.

Could well be true "sendthis"... it might well indicate a system that's overstocked, or under filtered...

But if all other parameters are normal... then a high nitrate reading usually means.. that the system is recently cycled... and/or there are insufficient plants to soak up the nitrate nutrients...

Nitrates in themselves... are not harmful to fish... unless they exceed levels of 450ppm+ (Bluegill)....

And the forum that was linked to... contains some totally misrepressented information... particularlly that posted with regard to "nitrates" causing "brown blood disease"... interfereance with haemoglobin...

It's not nitrates that cause that effect... it's nitrites...

http://www.sciencedirect.com/science/ar ... 8604006271

That's another one that hints at the accumulation of metals. I can't read it's conclusions or anything else at home so I might take a look at work. Anyway, it does indicate from the abstract that metal concentrations vary based on feed type as well.

I have no problem with the concept that metal accumulation within the flesh of fish might be an increased probablilty in RAS or aquaponics systems... due to their recirculating nature...

That's the very reason why we recommend minimising/eliminating the use of any products that might contain "metals"...

You're going to have to explain to me under-filtered. As far as I'm aware, there is only ONE major contributing factor to reducing nitrates (short of a WC) in an aquaponic system and that's the plants. If you're saying there aren't enough plants, then I would say, yes, I agree.

If you know of a good filter to remove nitrates, we need to talk and make some money.

There are anaerobic bacteria that remove nitrates as well as certain chemicals that will neutralize/bind with nitrate, but none are standard equipment in aquaponic setups.




Agreed... and I said a WC is a good fix to lower nitrates...



Again, my point wasn't to say it's "do or die".

However, there's plenty of research that indicates both sides of the story... as in everything, the real world is far more interesting and complicated. So I'll add to Bluegill...

http://www.sciencedirect.com/science/ar ... 3504009993

That article states certain inverts are sensitive.




I didn't post that link... I think that link was posted to disprove my point actually. I can't see that being mentioned in the link I posted.