Water levels

[Michael sanders]

I looked around the net today looking for real answers for water conditions for an aquaponics system.  I really did not find anything that I needed so I am going to ask the experts here.  I am sorry if it has already been answered. I have about 300 gallons and 35 1.5lbs tolopia, and about 120 fingerlings. I have checked the levels and they are the following:

Ammonia: .6
PH: 7
Nitrite: .5
Nitrate: 30
Temp: 68

I have (2) grow beds, (1) 4x5 by 10inch high, and (1) 4x7 by 10 inch high


I have seen that some say this these levels are fine, but really... what does it mean????


Any help would be greatly appreciated.

[Dan Brown]

How long has the tank been established? The Nitrate levels seems a little low, but if it's a new or heavily planted system that could explain it, or it could be your medium low stocking levels (judging your stock:water ratio), but it's better in my mind to understock than overstock as it's safer for the fish. Based on my experience and research, those water reading should fall well within the comfort zone for your fish.

[Sylvia Bernstein]

I agree with Dan that the levels all look within reason for a comfie situation for the fish, but I suggest you keep an eye on two things. First, I'm actually reading the Nitrate levels to be on the high side - mine typically run between 5 - 10. This tells me that you are underplanted for the amount of fish you have and the nitrates are building up. My other question concern is about the stocking levels for your tank. Ultimately you are looking for about a pound of fish for every 5 gallons of water or about 60 lbs of fish. You are at 52.5 lbs with the mature fish you have, and you have a young bio-filter so I would want you to stay there for a while...but then there are 120 more fingerlings to contend with....oh boy. How do you feel about having a neighborhood tilapia fry sometime soon?

[Sylvia Bernstein]

Hi Kobus. I haven't read UVI's literature, I"m chagrined to say, and far be it from me to question such esteemed work so I'm sure they are right. I'm reporting what I've learned through my own system, and going for the notion of balance. While the system may be able to survive very high levels of nitritate I wonder if it is best for the long term balance of the system - feels out of whack to me. Like I said, I've always run at about 5 - 10 ppm with my 12" media beds and everything grows like gangbusters. If it goes below 5 I figure I need to add more fish. But this is certainly less scientific than UVI...but also a different growing method with more bio-filter...

[Michael sanders]

Wow,

Thanks for all the input. I have the one 4x7 grow bed that is band new, not too many plants are planted in there either. I changed the system around again last night (Sylvia), so currently I have (3) bio filters on the system: The two grow beds ( I guess they are acting like a filter from what I have seen, and also a container with bio balls. The reason for the bio ball container is that with my NFT setup, the return from the NFT needs to be filter prior to it hitting the fish tanks (so I have been told) Doe this sound right? I want to use NFT just because I have it in place, and for space issues. The water levels should still be ok right?

[Dan Brown]

Nice reference Kobus, thank you. In your combined system, what readings do you shoot for (and what do you get)?

Sylvia, I was basing my estimation of nitrate levels on what Murray Hallam had mentioned regarding when it's time to add an additional bed. I believe he said that if nitrate readings are consistently over 300 ppm another bed is needed. I made what seemed to me to be a simple logic leap, and assumed his regular numbers were somewhere approaching that level (silly to make any assumption, I'm chastising myself as I write this) . I may have spoken too soon regarding stocking levels as well, your breakdown of stocking density is more detailed than my quick estimate, and is most likely far more accurate.

[Sylvia Bernstein]

Hey Kobus, no "smart ass"ness taken. I actually meant what I said and wasn't being sarcastic, although that is hard to read through a forum comment ;-) I really should read that paper, and I really am chagrined, and I really do hesitate to question their work. Thanks for posting it here...now I really have no excuse...


Kobus Jooste said:

Wasn't trying to ask a "smart ass" question :) The reason I asked about the paper was that I could not remember the levels off hand, just new that they were higher. They went over 50 mg/L in their rafts. Here is the paper for those that are interested.

Sylvia Bernstein said:

Hi Kobus. I haven't read UVI's literature, I"m chagrined to say, and far be it from me to question such esteemed work so I'm sure they are right. I'm reporting what I've learned through my own system, and going for the notion of balance. While the system may be able to survive very high levels of nitritate I wonder if it is best for the long term balance of the system - feels out of whack to me. Like I said, I've always run at about 5 - 10 ppm with my 12" media beds and everything grows like gangbusters. If it goes below 5 I figure I need to add more fish. But this is certainly less scientific than UVI...but also a different growing method with more bio-filter...

[Sylvia Bernstein]

Dan, I can't find that in my notes from Murray so I'll assume are right, but boy that seems mighty high, doesn't it? My API kit won't even go above 160. I'll see if I can get Murray's attention and ask him...


Daniel E Brown said:

Nice reference Kobus, thank you. In your combined system, what readings do you shoot for (and what do you get)?

Sylvia, I was basing my estimation of nitrate levels on what Murray Hallam had mentioned regarding when it's time to add an additional bed. I believe he said that if nitrate readings are consistently over 300 ppm another bed is needed. I made what seemed to me to be a simple logic leap, and assumed his regular numbers were somewhere approaching that level (silly to make any assumption, I'm chastising myself as I write this) . I may have spoken too soon regarding stocking levels as well, your breakdown of stocking density is more detailed than my quick estimate, and is most likely far more accurate.

[TCLynx]

I know of people who have never gotten a high enough nitrate level to really read it with the API kit and they still grow plants just fine.

My big system has usually tended to the rather high side on the nitrates. (As in I have to dilute the sample in order to get it down to a readable range and then do the math to figure out the actual reading.)

I've heard some talk that the high nitrate levels with the UVI method might have some to do with the pH adjustment methods they use.

I do believe that there is a correlation between pH and nitrate levels as the pH will affect how plants use different nutrients. The pH in my big system has stayed high due to the media. I've also watched the nitrate levels go up drastically after adjusting the pH up in my other systems.

A nitrate level of 30 ppm would not concern me either way though I think in a perfect world, that would be on the high side, my systems don't seem to know what a perfect world is.

I do agree about the concern that the fish load will be approaching the heavy side as the fish grow. Luckily they are tilapia but yea, it's gonna be time to start eating them soon.

[Sylvia Bernstein]

Well, I am convinced that I should stop worrying about Nitrates. You guys have made a convincing argument - thanks for enlightening me ;-). OK Mike, no more worrying about your system, except the need for that fish fry.

[TCLynx]

I didn't really comment on it before (and because you have tilapia which are pretty bomb proof it is probably no worries anyway) but I don't like to see measurable ammonia or nitrites in my systems. I grow catfish which are more sensitive to water quality though. If ammonia or nitrites get up to .25 ppm I start looking to see what might be wrong with my set up since seeing ammonia or nitrites usually means a build up of something or that the bio-filters are overloaded.

Since you say that you just changed things around and that you just added a grow bed, then I might guess that to be the cause of the ammonia and nitrite readings but if they don't go away, all the more reason to eat some fish soon.

[Sylvia Bernstein]

His system is also very new, TC, so that might explain some ammonia.


TCLynx said:

I didn't really comment on it before (and because you have tilapia which are pretty bomb proof it is probably no worries anyway) but I don't like to see measurable ammonia or nitrites in my systems. I grow catfish which are more sensitive to water quality though. If ammonia or nitrites get up to .25 ppm I start looking to see what might be wrong with my set up since seeing ammonia or nitrites usually means a build up of something or that the bio-filters are overloaded.

Since you say that you just changed things around and that you just added a grow bed, then I might guess that to be the cause of the ammonia and nitrite readings but if they don't go away, all the more reason to eat some fish soon.

[RupertofOZ]

Just a couple of points regarding nitrates...

It's quite common in a mature system with an appropriate level of filtration and stocking... to have a zero nitrate reading...

I't doesn't necessarily indicate any problem... just an indication that the plants are using all the nutrients available.

If you have a zero reading and your plant growth appears to be struggling, then it probably indicates that you may need more fish...

But generally people, if anything are over-stocked... and a reading above 80-100 would indicate that more plants could be planted...

Any reading above 150+... would probably indicate that you do need to add extra grow beds, as you obviously would have maxed out your existing beds...

But to my mind, it also probably indicates that you need to do so because your feed load and stocking level is exceeding your filtration capacity anyway...

N.B. ... I'm talking a mature system as opposed to a relatively new system with new, or recently planted plants... where it is possible to see nitrate levels above 150+, particularly if the system has just completed fishless cycling with urea or hummonia... often where initial ammonia levels may have exceeded 4-8....

In terms of fish health and nitrates... despite extensive research during the 4 years of my aquaculture studies...

I have not been able to find any references to nitrate toxicity below 450-500 ppm (bluegill)... with most indicating levels approaching 1500-2000 ppm...

And this was recently confirmed here in Australia by Dr, Wilson Lennard during a seminar...

I'm certainly not advocating the levels above 100 ppm are in anyway desirable... on the contrary, to me they probably indicate a general system imbalance...

But merely pointing out the nitrates levels, in general... just aren't a concern...