Cecil's progress of recirculating Aquaculture System

[Cecil]

Gary has suggested I set up a thread where i can update the progress of my first experiences with an RAS I set up in early winter. I have four oudoor ponds on the property but the RAS experience is brand new to me.

As a refresher here is the 300 gallon epoxy coated stock tank I set up, with the 600 square feet of surface area RBC I built. There is also a 55 gallon drum clarifier with a 'U'-Tube siphon which pulls water out of the tank via a siphon action and puts it under a dense layer of fine mesh. The water is pulled out of the clariifer with a small 5 gpm pump that sits on top of the fine mesh. This goes to the RBC, which rotates by the water dropped on the center baffles. Suspended particles are trapped under the fine mesh nettting and there is a drain in the bottom of the clarifier barrel to periodically drain the clarifier barrel after spraying down the mesh for cleaning. The 'u'-tube is simply capped on the clarifer end and pulled out and set over the tank wall during cleaning. There is no need to re-initiate the siphon action if it's done in this way.

Special thanks to Steve VanGorder and his book Small Scale Aquaculture that showed me how to build the RBC etc.

[Cecil]

Update; February 2, 2010


Finally my system has cycled!

Now along with the ammonia in my fishless RAS my nitrites have finally dropped to zero. Today it was time to add the fish.



So finally today after a long wait it was time to get the fish out of a frozen pond that were being held in a floating cage.

Here are a few holes in the ice in the top of the cage to make a larger hole to net out the bluegill fry (fall spawn and are only about 3/4 inches.) Note the jugs for flotation are inside the cage. That's because the mesh is so fine it tears easily, and I didn't want to take a chance of having a hole ripped in the mesh and fish escape. So the jugs were attached inside to the vertical post vs. outside through the cage mesh.





Here I have made one big hole by using an ice spud. The ice was about 6 inches thick.





The fish were dipped out of the cage and brought in via a five gallon bucket. I then dipped and sorted the live ones from the dead ones with an aquarium net. I believe I had about a 50 percent mortality rate in the cage, but that still leaves me with several hundred to a thousand for the RAS tank. I believe if these fish would have been an earlier hatch and larger, they would have had a higher survival rate. My earlier hatched fish are in another cage in the another pond and are much larger.

Here are a few live ones in the aquarium net with a couple of dead ones.





I filled a 55 gallon drum with pond water and added salt to a 2 ppt or a 0.2 percent solution. The plan is the water will slowly warm up to the RAS tank temp before adding them to the RAS tank. As you can see I suspended an agitator above the tank. I've since unplugged it as it may be stressful to the fish by causing too much turbulence. The fish are weakened state coming out winter temps. I'm keeping an eye on D.O. and if it gets too low will crank it back up.






Although heating air to heat a fish tank is very inefficient I've decided to give it a try as the furnace is running anyway, and i can't afford a submerged heater right now. The room the RAS tank is in is only 14 by 7 so it's not like I'm heating a large space. I've blocked it off with plastic to keep the heat in and diverted a vent to the middle of the fish tank room. I also shut off some vents to my taxidermy shop and front room as I don't need it warm down there anyway. It's raised water temps in the 330 gallon system two degrees in two days.





Whatever I can get the water temp up to will increase the effeciency of the biofilter and the fish will grow faster. Time will tell.

[Cecil]

About 28 hours later the initial 35 F. water ( ~ 2.0 C.) in the acclimation barrel had warmed up to 59 F. (15.0 C.). Frankly I was surprised it warmed up that fast especially since I hardly ran the agitator and the air temp is only about 65. F. (~18 C.) That was about 4 degree F. less than the water in the RAS, but I decided to go ahead and move them tonight as the ammonia in the acclimation barrel had spiked to 0.5 mg/l. I felt as the water warmed and their metabolism was increasing rapidly I needed to get them in their new home and on feed ASAP. These fish had basically been on a fasting mode for at least a couple of months under the ice.

Here are less than half of the fish left in the acclimation tank before being scooped up, dipped in a clear clean soluton of 2 ppt or .2 percent NACL and them released into the tank. I'm estimating I have up to 1000 3/4 inch fry in the RAS tank.



My mission now will be to get them on feed ASAP and to put back on weight and start growing again.

[Cecil]

Well I've learned three things recently:

1.) My Hanna Low Ammomia Range Ion Specific Meter reads erratically when there is iron in the water. I called the company to find out how the iron effects it, and that is what they told me. I was wondering why I was getting wildly different readings after my Culligan Iron filter isn't working as well!

So I'm depending on my chemical tests instead when I've got temporary iron issues with water make up. Fortunately the iron is removed within a day via the clarifier which makes the tank water swimming pool clear. Then I am confident of the reading with the spectrometer (Ion Specific Meter) if they coincide with the chemical tests. However due to the fact that these fish are so small with very fine gills, I think I will drain a little and add a little water at a time on a continuous basis vs. one big change now and then until I can use iron free water. Iron can be quite irritating to gills as it's sharp edged.


Can't wait to get my second pump and use two drums in tandem with a siphon and netting like my clarifier to remove the iron mechanically.


2.) Apparently the nitrobacters are not working as well in the cold water as the nitrosomonas as I keep getting a reading of about .25 mg/l nitrites are a little less. Ammonia is 0.0 or close to it. I did a 50 percent water change the other day to play it safe.

3.) I've been overfeeding them. I know that because I removed a fair amount of feed underneath the RBC. I try and remove any feed that is on the bottom of the tank. Unfortunately floating feed is not an option at this size. I need to remember the water is only 62 degrees! The next time I set this up I'm going to set up a venturi drain in the center and get some kind of minor circular flow to get wastes to gravitate toward the drain.

[Cecil]

Update:

The bluegill have added about a quarter of an inch since I put them in the tank February 2nd, even at water temps of only 62 F.
Here's a pic of some of them at feeding time. The water is not green at all. Apparently the flash on the camera makes it appear that way.




I've decided to feed them a little at a time several times a day vs. a heavier feeding two or three times a day. At this size the fish need to feed often for maximum performance, although of course, the cooler water is holding them back a little. Fewer heavier feedings seems to waste feed.

I did a 50 percent water change this morning to see if it would effect the nitrites which are holding at .25 percent. No change yet but the fish appear healthy and feeding with only a loss per day up to five fish out of about 1000. Salinity is about 0.20 percent to 0.21 according to how much non-iodized table salt I'm adding and my Koi salt meter.

I also bought fresh feed today (Aquamax 5D01) My other 5D01 is almost a year old and I don't want to take chances of any vitamin deficiencies, especially vitamin C. According to a fish pathology book I have vitamin deficiencies cause deformities in young fish including scoliosis and other spinal deformities. Unfortunately the 5D01 is not cheap at 50 percent protein. $41.00!

[arachdog]

I did a 50 percent water change this morning to see if it would effect the nitrites which are holding at .25 percent. No change yet but the fish appear healthy and feeding with only a loss per day up to five fish out of about 1000. Salinity is about 0.20 percent to 0.21 according to how much non-iodized table salt I'm adding and my Koi salt meter.

.25% ?? I'm sure you haven't got that right, that would be invariably fatal to any fish. I'm not sure what you nitrite levels really are ,but nitrite isn't something to toy around with. If they are high then I'd be doing 20% regular daily water changes until it was under control, especially if you are getting daily mortalities.

[Cecil]

.25% ?? I'm sure you haven't got that right, that would be invariably fatal to any fish. I'm not sure what you nitrite levels really are ,but nitrite isn't something to toy around with. If they are high then I'd be doing 20% regular daily water changes until it was under control, especially if you are getting daily mortalities.

Whoops my bad! I meant 0.25 mg/l!

Interestingly my fish pathology text says sunfish are rather tolerant of nitrites.

In contrast sunfish tolerate high levels (96 hour LC50 often > 50 mg/l) because they do not actively take up nitrite from water.

Fish Disease Diagnosis and Treatment - Edward J. Noga

[arachdog]

Oh OK, no worries, easy mistake to make. .25mg/l doesn't sound too bad. I didn't know sunfish were so tolerant of nitrite however it should be noted theres a going to be big difference between what it takes to kill 50% in 96 hours and optimum conditions. I'm only guessing but its possible that prolonged immersion in even .25mg/l is enough to cause some stress and increase your mortalities. To be honest I've also go no idea of what the typical death rate for sunfish of your size and condition, maybe daily deaths are unavoidable.

Also sorry to criticize your bio-filter again but I thought it was worth mentioning that modern RBC have moved away from the corrugated plate design. Instead they use woven nylon discs similar to pot scrubbers, this gives them far more surface area for a given sized wheel.

[GaryD]

Hi

While I'm interested in how RBC's function, I much prefer trickling bio-filters for cheapness and reliability.....and they provide for excellent aeration while facilitating nitrification.

Gary

[Cecil]

Also sorry to criticize your bio-filter again but I thought it was worth mentioning that modern RBC have moved away from the corrugated plate design. Instead they use woven nylon discs similar to pot scrubbers, this gives them far more surface area for a given sized wheel.

Criticize all you want as long as it's constructive.

Sounds like you are referring to a biodrum which also rotates but is full of discs and has more surface area. I plan on building a smaller plastic mesh drum for a large aquarium show tank in my taxidermy studio. It will have plastic media inside packed around the axle and contained by the plastic mesh. I have extra plastic media from a packed column I built for my well water.