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Solids in DWC systems and Gammarus

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?

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Replies to This Discussion

Permalink Reply by Sahib Punjabi on November 7, 2011 at 7:48am

Hello Gina,

I have them in my Koi pond filters. This is an external pond and has been in operation for many years. I first noticed them after about a year of operation and was not sure what they were. I would try to change filters often so as to get rid of them. It was only after reading the Friendly's Micro Systems Manuel that I was able to learn what they were and what a valuable task they were performing. They occurred naturally and I have no idea how to replicate them. I have not cleaned my filters at my small aquaponics research farm for some time. Next time I do, I will share if I noticed some and post pictures.

God bless

Permalink Reply by Mark Rhine on November 7, 2011 at 8:01am

Yes Gina, we have thousands of them. We seeded our system about three months into operation, thought we had lost them. During one of our net tank cleanings we discovered a huge population. Once we knew what to look for, we found them in our trough bottoms, in the fallen cocotek, and in our "rock boxes" or you guys call them media beds. They also live in the muck in our solid settling tank. We see them when we evacuate water out of the solids tank for our fish fertilizer. We suspect they are living though out our system, although it is unlikely they are living in the rearing tank.

Permalink Reply by TCLynx on November 7, 2011 at 8:27am

I actually seeded some into my system but since I'm running mostly media beds, I'm not sure I would be likely to find them again if they were there or not.

Now I do know that there are other little creatures here in Florid that can fill the same niche. Sometimes to the owner's dismay actually.

Let me recall an encounter at the Aquatic Ecosystems Counter.....

So there was a lady there with a jar of fairy or ghost shrimp asking how to get rid of them in a koi pond system. She was the person taking care of maintaining the koi pond for the owners. See apparently the tiny shrimp had taken up residence in the filter pads of the skimmer box and were eating the detritus which was actually leaving the filters too free flowing. Basically there were lots of too small particles getting through the filters now cause the shrimp were keeping the filter pads too clean. Now to us in aquaponics this seems like a great thing but for the owners of the koi pond who want crystal clear water with now tiny floating detritus it was a bad thing. Sad thing but I expect that pond gets dosed weekly with a product that will kill crustations but not harm the koi but allow the filter pads to clog up enough to catch the finer detritus and require the maintenance person to clean the filter pads every couple weeks since the shrimp won't be there to do it for them.

So while we may or may not be able to support gammarus, I expect there is something that will fill that niche here in Florida.

Permalink Reply by Gina Cavaliero on November 7, 2011 at 8:32am

Sahib what is your pH in your Koi pond? I would expect that at least our "outside" system to have been populated, but there is still nothing there after nearly a year and a half. We did some research on them some time ago, to try to determine how they just occur and never did find a definitive answer. Do you know what your total dissolved solids are either? Our well water is nearly distilled at only about 25ppm solids, which I attribute to our elevation, a whopping 180ft above sea level, but that translated into a very deep well with lots of filtration as opposed to most in Florida. Maybe there is something lacking in this water that the gammarus need to thrive. Mark, how about your pH or TDS?

Permalink Reply by TCLynx on November 7, 2011 at 8:48am

I do know most crustations need a good amount of calcium carbonate (and perhaps some other minerals) to form their shells so your water may be far better for growing plants by feeding fish but less helpful for creating an ecosystem including crustations. Do you guys get snails? I have intense numbers of snails eating detritus in my systems.

Permalink Reply by Sahib Punjabi on November 7, 2011 at 9:02am

You know Gina, I have not checked that in a while. It was around 7.00 when I last checked according to the test strips and the liquid tests. I will check in the next day or two and share that info. As regards total dissolved solids...no way I can tell you. I do not have a meter or way to test for that. All I can say is that my Koi pond is very heavily oxygenated and I do not appear to have any problems with my home aquaponics system or my fish - some of them being almost 3 ft long :-)

God bless,

Gina Cavaliero said:

Sahib what is your pH in your Koi pond? I would expect that at least our "outside" system to have been populated, but there is still nothing there after nearly a year and a half. We did some research on them some time ago, to try to determine how they just occur and never did find a definitive answer. Do you know what your total dissolved solids are either? Our well water is nearly distilled at only about 25ppm solids, which I attribute to our elevation, a whopping 180ft above sea level, but that translated into a very deep well with lots of filtration as opposed to most in Florida. Maybe there is something lacking in this water that the gammarus need to thrive. Mark, how about your pH or TDS?

Permalink Reply by Gina Cavaliero on November 7, 2011 at 9:13am

Interesting point TC. We do add calcium carbonate, but probably not near enough to support crustacean growth or proliferation. I suspect that the mineral content is the determining factor here. We do not get snails either. Not a one. But don't you think that somehow perhaps in a fish shipment, you may have brought those in? But, back to the Gammarus, that was what I was wanting to identify in this discussion. What might be the difference why some systems support Gammarus populations and others do not. I know of several other systems that have been operating as long or longer than mine, but no Gammarus and this is in many other places around the country, not just Florida. I think it is safe to say that we cannot expect the presence of Gammarus to be a universal in aquaponic systems. As much as I would love to, I can't rely on them for solids removal in my systems as they only exist under certain conditions. It would be interesting to test water samples from systems that have and don't have to really identify where the difference lies. There's that pesky testing again! Sigh... We just need our own private aquaponic lab!

Permalink Reply by TCLynx on November 7, 2011 at 9:46am

Yea, a lab and a few handy scientists and lab assistance with some great gadgets. (Wouldn't it be great if we could have our very own Aquaponics Abby? LOL guess what TV show is on in the background much of the time in my house.)

Yes, it would be cool to identify the differing water chemistry for Gammarus and whatever other creatures we might find to fill that niche.

However, I do thing you guys are onto something by adding a BIG media bed to take care of your solids mineralization and avoid the whole having to clean out the solids regularly.

Permalink Reply by Gina Cavaliero on November 7, 2011 at 1:02pm

Maybe some day TC we can have our very own AP Abby. And thanks for that. I think we are on to something with a BIG media bed too. Kind of a natural progression to optimizing the system. We are very excited about it. Tonya just did the dirty deed last Friday and I would say she is VERY excited about it! LOL!

Sahib, maybe I can get my TDS meter to you somehow for you to play with and we could compare. Would be interesting!

Permalink Reply by Sahib Punjabi on November 7, 2011 at 3:14pm

Sure...love to see what results I get :-)

God bless,

Gina Cavaliero said:

Maybe some day TC we can have our very own AP Abby. And thanks for that. I think we are on to something with a BIG media bed too. Kind of a natural progression to optimizing the system. We are very excited about it. Tonya just did the dirty deed last Friday and I would say she is VERY excited about it! LOL!

Sahib, maybe I can get my TDS meter to you somehow for you to play with and we could compare. Would be interesting!

Permalink Reply by TCLynx on November 7, 2011 at 3:55pm

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.

Permalink Reply by Sahib Punjabi on November 7, 2011 at 7:14pm

Yeah :-)

You are welcome any time TCLynx.

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.