Solids in DWC systems and Gammarus

[Gina Cavaliero]

Operation of our DWC system over time has lead us to the conclusion that for small scale aquaponic farms that much can be gained from integrating media beds as an efficient mechanism for handling the solid wastes produced in the system.  Even with low density, the lack of solids removal as in our small system is still problematic and the deposit of fish waste into the trough over time eventually becomes a substance that needs to be removed.  Systems that rely on more effective, but also somewhat more costly solids removal such as drum and swirl filters seem to manage the waste better in DWC, however there is still the aspect that the valuable solids do not stay in the system.  

Systems in Hawaii have tiny crustaceans called Gammarus appear in their aquaponic systems after about 6 months that eat or metabolize the fish waste.   We know of several systems in Hawaii where after roughly the same amount of system operation time, the Gammarus just "appeared".  Both of our systems have been running well over this time frame and we have not had Gammarus appear in ours. In fact an attempt to populate a small system with them failed.  Temperature or pH related perhaps?  Or does this crustacean thrive only in certain environments or eco-systems such as Hawaii or with conditions similar to Hawaii?  We do know that the mineral content in the water in Hawaii is drastically greater then the mineral content of the water in Florida.  TDS tests indicated the particulant content was several hundred times greater.  Maybe this is another factor.  

Does anyone know of a system outside of Hawaii where Gammarus population has occurred intrinsically or where there was a successful seeding?  

[Meg Stout]

So it seems most folks have gammarus, except for poor Gina, who wants them...

 

What would be a good way to be certain I have them (other than assuming my system is being cleaned by gammarus instead of magical fairies)? Drop of water on a slide under a microscope?

[Mark Rhine]

Get a big magnifying glass, grab a handful of muck out of your system, throw it on a board a look for little shrimp swimming in circles. You will see them if they are there...

Meg Stout said:

So it seems most folks have gammarus, except for poor Gina, who wants them...

 

What would be a good way to be certain I have them (other than assuming my system is being cleaned by gammarus instead of magical fairies)? Drop of water on a slide under a microscope?

[Sahib Punjabi]

Spot on TCLynx :-)

 

I too have read and been advised the same  Most TDS meters are really not effective in Aquaponics as they are in Hydroponics, hence I never invested in them. My basic strip tests (not done too often, maybe once a month unless I have some major issues or events), have been adequate so far and after over 11 years of having Koi ponds, lots of mistakes and disasters, I have come to know the water chemistry pretty well...you know it is time to clean your filters when you start to get cloudy dirty water or that something is wrong when you have a strong fishy smell or dead fish that you cannot explain. So far, my experience and gut feel has worked just fine :-) Now there may be a need for the large commercial Aquaponics systems, which I certainly am not, for such constant testing.

 

Still, I am willing to learn something new. Perhaps there are new designs of such meters that are more appropriate for Aquaponics. Would love to see what your meter come up with:-)

 

By the way, not only do I have Gammarus, but also some other type of shrimp looking creatures and lots of thin red worms plus some that are pretty fat and almost black in color. Good Bio stuff I guess :-)

 

God bless,

TCLynx said:

One issue I have with most tds meters is that they really are only telling you the conductivity of the water and guessing what that means in relation to hydroponic nutrient solutions.  It doesn't necessarily tell you how much minerals are in your water but more likely how much salt.  I expect in HI they have a bit more salt in their water.  My well water is very hard with lots of calcium carbonate but it doesn't read very high on the TDS meter, it actually reads higher on the TDS meter if I use the water softener since the water softener tends to add a trace of salt since the beads rarely rinse completely.  (by the way the water softener really hasn't been in use since we moved in but I did comparison tests when we first moved in since I was doing hydroponics then.)

 

What TDS meter do you have Gina?  I have a bluelab truncheon I could perhaps bring it with me when I manage to get over to see Sahib sometime soon, which I've been planning on for a while but other things keep getting in the way.  (Maybe this coming weekend?)

 

Anyway.  Your water is quite a mystery to me Gina, perhaps there is a good layer of peat soil somewhere that it filters through before it gets down to the aquifer you are drawing from.

[Gina Cavaliero]

I have an ExStik.  It measures four parameters—conductivity, TDS, salinity and temperature.  True that they are designed for measuring mainly salinity in Hydroponic systems, however interestingly mine shows a higher reading in my system water then my well water.  Which I would have to assume as a true indicator of something other than salinity(actual solid content) when taking a solids reading.

 

As far as my well water being mystifying TC, I completely attribute it to my elevation.  I have never had to drill a well in Florida much deeper than 40 to 60 feet anywhere else I have lived.  Here though when the existing pump died the day after I closed on the property, arrghh, I had to put in a new one and they went to 221ft to hit water.  There must be an additional layer of filtration I am getting that also contributes to my unique pH.  I think we have discussed before, I am at 6.5, whereas most everyone else in Florida is above 7.  You are about 7.5, right?    

Mentioning test strips and testing though.  We were of the opinion before that test strips were adequate for accurate testing and not only are they more costly, but they do not always give accurate or consistent results.  We surmised this and started pulling two to three at a time to insure we received the same reading and we always didn't.  When Sylvia and Murray where here, they also were surprised that's what was being used and advocated.  Since then we have converted to a test kit sold at the Aquaponic Source and for $24, it tests all four things and provides more tests (haven't determined yet exactly how much more, but believe it will be significant).  We were using as advised 5 different types of test strips that totaled greater than $50 but only provided 50 tests.   The test kit does take a little longer, but not significantly enough more compared to the cost savings on the strips and it is considerably more accurate.  

 

 
Sahib Punjabi said:

Spot on TCLynx :-)

 

I too have read and been advised the same  Most TDS meters are really not effective in Aquaponics as they are in Hydroponics, hence I never invested in them. My basic strip tests (not done too often, maybe once a month unless I have some major issues or events), have been adequate so far and after over 11 years of having Koi ponds, lots of mistakes and disasters, I have come to know the water chemistry pretty well...you know it is time to clean your filters when you start to get cloudy dirty water or that something is wrong when you have a strong fishy smell or dead fish that you cannot explain. So far, my experience and gut feel has worked just fine :-) Now there may be a need for the large commercial Aquaponics systems, which I certainly am not, for such constant testing.

 

Still, I am willing to learn something new. Perhaps there are new designs of such meters that are more appropriate for Aquaponics. Would love to see what your meter come up with:-)

 

By the way, not only do I have Gammarus, but also some other type of shrimp looking creatures and lots of thin red worms plus some that are pretty fat and almost black in color. Good Bio stuff I guess :-)

 

God bless,

TCLynx said:

One issue I have with most tds meters is that they really are only telling you the conductivity of the water and guessing what that means in relation to hydroponic nutrient solutions.  It doesn't necessarily tell you how much minerals are in your water but more likely how much salt.  I expect in HI they have a bit more salt in their water.  My well water is very hard with lots of calcium carbonate but it doesn't read very high on the TDS meter, it actually reads higher on the TDS meter if I use the water softener since the water softener tends to add a trace of salt since the beads rarely rinse completely.  (by the way the water softener really hasn't been in use since we moved in but I did comparison tests when we first moved in since I was doing hydroponics then.)

 

What TDS meter do you have Gina?  I have a bluelab truncheon I could perhaps bring it with me when I manage to get over to see Sahib sometime soon, which I've been planning on for a while but other things keep getting in the way.  (Maybe this coming weekend?)

 

Anyway.  Your water is quite a mystery to me Gina, perhaps there is a good layer of peat soil somewhere that it filters through before it gets down to the aquifer you are drawing from.

[TCLynx]

If I let my well water air out before I test the pH, I'll get a reading of 8 or higher normally here (same was true of my city water where I lived before too.)  If I just test the pH straight out of the tap it gives a false low of about 7-7.5.  My Well pump is at 126' down.

 

Yea, the test strips are not generally all that consistent/accurate unless you get the really $$ ones and keep them under strict temperature/humidity control until use and use fairly quickly since I think they deteriorate with age as well.

 

The test tube and dropper kits may seem like a pain but it really isn't so bad and the pH tests don't require multiple re-agents or waiting the 5 minutes so are really fairly easy to use.  I like to think, If it's Green it's good for the regular range pH test.

[Dave Lindstedt]

Hi Gina:  After attending your 1 day class on May 15th,  I spent the next 4 to six weeks in construction.  Big deal and major learning experiance was construction of a self built 330 gal. tank, from 2 x 4, plywood & pool liner. I did not take in consideration water weight of 8.3 lbs per gallon.  Long story short we kept blowing out seems.  Finally reinforced my 4ft x 4ft x 3ft (H)  tank with 1/2 inch steel banding straps. July 20th drove down to Myacka City and purchased 220 fish.  I now have 4 32sq.ft grow troughs growing well.

As I am looking to go commercial and in the process of expanding to additional 750 gal of tankage combined with 20 additional grow troughs and construction of a 24ft (W) x 36ft or 42ft green house.  So here is my question.... What crops have proven to be most profitable to you? 

[Chris Smith]

Hey Gina, I have populated my systems  with gammarus from Friendlies. My populations have never reached the numbers that I have seen in several other systems in the area. I have them in my systems but I have never been able to rely on them to clean net tanks. That is why I switched to media/worms long ago.

I have seen a few systems where the gammarus populations got out of control where they ate roots and foliage that touched the water. In these systems the gammarus caused so much root damage that the plant growth was stunted. In one system the gammarus was eating into the bottom side of the foam while eating the bio-slime. The foam developed sever pitting on the bottom side only.

[Gina Cavaliero]

Hey Chris.  Thanks for the info.  I do think they are unique in certain systems for some unexplained reason.  Again, perhaps calcium or mineral levels or pH?  That is why I don't think DWC systems without an efficient mechanism for solids removal work well, unless you are lucky enough to have Gammarus to eliminate the solids.  Exporting solids to media beds and worms definitely makes sense.  You know that is what we are doing as well now.  We are also doing this in our small system as we have had the same issues there as the Gammarus never showed up to remove the solids for us and their staying in the system started causing issues.  

 

I have heard of the problems you mention with the Gammarus in other systems.  Do you think that started occurring because if the system is conducive for Gammarus population, that they will overpopulate and exceed the systems' waste producing capacity to feed them?  Interesting!  

 

 

 

[Damon Polta]

the thing with the gammarus naturally appearing is that they need a natural way into the system.

 

more often than not they make their way into the system by falling off of birds that land in a near by water source.

 

another way in would be poor filtration of water introduced into a system from a near by water source.

 

if you have your system completely greenhoused in, i wounldnt be expecting gammarus to appear naturally.

 

these little guys are found literally everywhere. there is some form of gammarus where ever a naturally occurring water source occurs, 

 

sooo.... unless you're going to transplant them directly into your system that is boxed is by a green house, i'd suggest to open a window and let the birds in.

[wes]

I dont have anyway to prove this but my gut says to me that some how they can come from the dirt in the potted plants you may have purchased to put into your system. I have a small greenhouse 11 by 20 and my DWT  system had gammarus in it about 4 months after we started with the system back in march of 2011.

Damon Polta said:

the thing with the gammarus naturally appearing is that they need a natural way into the system.

 

more often than not they make their way into the system by falling off of birds that land in a near by water source.

 

another way in would be poor filtration of water introduced into a system from a near by water source.

 

if you have your system completely greenhoused in, i wounldnt be expecting gammarus to appear naturally.

 

these little guys are found literally everywhere. there is some form of gammarus where ever a naturally occurring water source occurs, 

 

sooo.... unless you're going to transplant them directly into your system that is boxed is by a green house, i'd suggest to open a window and let the birds in.