Trout in an RAS

[Cecil]

For those of you that grow out trout in your systems do you do anything more intensive with particulate management vs. other species? If so what do you do? Obviously lower temps and a good supply of oxygen are paramount. Do any of you increase surface area of you biofilter(s) to compensate for lower temps?

I'm thinking of growing out trout in an RAS vs. outdoor flow through pond in a year or two, possibly in a level below ground of a building to keep temps low.

?

[Cecil]

No one?

[GaryD]

Hi Cecil,

I can't keep trout in my state but from my reading about the experience of others, clean water seems to be important with trout (certainly more so than native species like jade and silver perch). Their need for high DO levels is accommodated by the fact, as you're aware) that cold water holds more oxygen than warm water does.

I'll leave the matter of bio-filtration to someone with more experience of trout than me......but my general approach is to keep adding bio-filtration until it will cope with the amount of feed that I want to feed (based on what the fish will take). If you are getting other than trace ammonia levels, that should indicate a need for more bio-filtration. Fortunately, I use trickling bio-filters and (more recently) moving bed bio-filters, so adding more bio-filtration is a relatively simple thing to do.

Gary

[kellenw]

Cecil,
If I was going to raise trout in high densities, and had the money to invest, I would look into drilling a 100 foot U-tube system. It can concentrate DO at about 1 additional ppm per foot of depth using atmospheric pressure. Must be at least 33 feet deep to get any real benefits for the most part. From studies, it seems like 300 feet of depth is about the cap and it loses efficiency beyond that.

[Cecil]

Makes sense but I don't want to grow them in high densities as much as I want to produce high quality fish with excellent fins that I can get a premium price for. I know this can be problematic in tanks but it's been done with brook trout recently in northern Wisconsin. Max annual poundage would be about 1000 lbs.

I could grow out some trout for a local trout club (fins not as important there) in addition to this if they have trouble getting any (which they are now due to disease issues at one of their suppliers) but that wouldn't exceed 2000 lbs. annually.

I'd prefer to build all my own components and probably use swimming pools for tanks.

[Cecil]

Hi Cecil,

I can't keep trout in my state but from my reading about the experience of others, clean water seems to be important with trout (certainly more so than native species like jade and silver perch). Their need for high DO levels is accommodated by the fact, as you're aware) that cold water holds more oxygen than warm water does.

I'll leave the matter of bio-filtration to someone with more experience of trout than me......but my general approach is to keep adding bio-filtration until it will cope with the amount of feed that I want to feed (based on what the fish will take). If you are getting other than trace ammonia levels, that should indicate a need for more bio-filtration. Fortunately, I use trickling bio-filters and (more recently) moving bed bio-filters, so adding more bio-filtration is a relatively simple thing to do.

Gary

Sounds good to me Gary!

[kellenw]

As you mentioned in the original post, you are going to need to focus on removing those micro solids suspended in the water column in a far more serious way than you would for your bluegill. Probably need two mechanical "pre" filtration stages. One down to about 250-300 microns and then following that down to about 50 microns. Really the only reason for the first mechanical filter is to reduce the amount of work cleaning the micro fines filter, which it WILL help tremendously with that.

[AChaplinski]

Howdi,
I've got a CHOP setup with 2 1000L fish tanks, 1 1000L sump, 4 1800 x 1000mm growbeds, 200L swirl filter and a box filter on return to sump.
I'm pleased to say that I've successfully grown out 50 trout to plate size since March. I feed them twice a day and they grow fast!
Although it's gone well, I've had to clean the top third of my swirl filter almost daily and vacuum the fish tanks twice a week.
Extra filtration will make my system more efficient and I will improve things once I've harvested the last 13 fish.
Andy

[Cecil]

As you mentioned in the original post, you are going to need to focus on removing those micro solids suspended in the water column in a far more serious way than you would for your bluegill. Probably need two mechanical "pre" filtration stages. One down to about 250-300 microns and then following that down to about 50 microns. Really the only reason for the first mechanical filter is to reduce the amount of work cleaning the micro fines filter, which it WILL help tremendously with that.

So would the clarifier I'm using now work for the first stage? If so, what about after that clarified water feeds to the biofilter paddles and tank, I siphon it to another drum clarifier and then pump this water through something like a cartridge filter back to the tank, which also creates a circular motion in the fish tank to allow it to "self clean" to the center drain?

If not this what do you specifically suggest?

[Cecil]

Andy,

Can you give more specifics on the swirl filter? How are the fins on your fish? I hear that can be a problem in fish tanks which is something I will want to avoid. I'm hearing more frequent smaller feedings help avoid the fish pecking at each other's fins. Also very smooth tank walls.

[AChaplinski]

Well, now that you mention it, I have noticed the occasional 'gap' in some fishes tailfins.
I didn't think much about it. I guess being new to keeping fish in the backyard, it didn't occur to me that they were nipping each others tails.
So that's what all the splashing's about!
My swirl filter is very similar to Davoponics drum filter. I believe a narrower drum with a conical base would be better but how to make a conical base and connect it to a cylinder cheaply and efficiently is the problem.

[AChaplinski]

my apologies for entering into this thread. I now realize what a RAS system is and mine is'nt one.

[Cecil]

Actually there are other causes and your fish may have already had that gap when you got them but you didn't notice.

Since in my one market it's imperative that fish have perfect fins I'll probably start from eggs and eliminate any possible reasons for poor fins.

My market is exclusively for male fish so I may actually treat the fry with a male hormone laced feed to produce all males. My fish are not destined for the food market.

[Cecil]

my apologies for entering into this thread. I now realize what a RAS system is and mine is'nt one.

Oh no you're fine. As long as you are raising fish you're in! :D I appreciate the information too!

[kellenw]

So would the clarifier I'm using now work for the first stage? If so, what about after that clarified water feeds to the biofilter paddles and tank, I siphon it to another drum clarifier and then pump this water through something like a cartridge filter back to the tank, which also creates a circular motion in the fish tank to allow it to "self clean" to the center drain?

If not this what do you specifically suggest?

For the first stage, I would go with a sieve bend filter using a 250 micron stainless steel screen (you could range from 200-300 micron). AES sells a pre-made sieve filter (Cetus sieve), but it's ridiculously expensive (as are all manufactured sieve filters unfortunately). See http://www.aquaticeco.com/subcategories/3868/Parabolic-Screen-Filter-CETUS-Sieve. However, one can be DIY'd fairly easily. Wedge wire would be ideal for the screen material, but it's extremely expensive. Standard steel screen will work as well, but you'll have to use a brush on the screen every 3 weeks or so because it will slowly become coated with bio slime (wedge wire doesn't have this problem). The advantages of sieve filters are pretty huge in my opinion. They are "self cleaning", do not waste water, pull solids completely and "instantly" out of the water rather than holding them in filter media that remains in the water and that must be cleaned and/or backwashed frequently. This substantially improves water quality since the solids aren't just sitting in the water and leeching ammonia until you clean the filter. The second stage could be filter socks at about 50 microns. You'll have to routinely clean them, but that's easy enough, and with the sieve pre-filter, it won't be too bad. This will really polish your water. THEN, following the sock filter (fines filter), I'd run to my barrel. I would fill the barrel full of pot scrubbies (cheaper than kaldness, bioballs, etc. and arguably more surface area too) and place a high output airstone in the bottom. This will act purely as a biofilter, and since you've pre-filtered all the nasties , will require virtually zero maintenance. Further, the entire thing could be gravity fed, only requiring a pump for return water.

For the fish tank(s), I'd go with an 8x2 foot circular stock tank (~640 gallons per tank). I would install a central drain with a hood, with a disc type 6-8 inch air diffuser/stone mounted just above it. This will cause the water to circulate in such a fashion that solids will push up and out toward the outside walls of the tank and then sweep across the floor of the tank toward the drain (like the effect an air diffuser style pond aeration system has). This will ensure solids are quickly removed from the fish tank with minimal water flow requirements. Overall, it will be far more efficient than relying on water alone to direct solids to a drain.

Hope I made sense Cecil. I typed this up really fast at work. Let me know if you have questions. I'm going to be building a couple of sieve filters in the next several weeks, so I'll have plenty of firsthand build experience to share... hopefully all good... hehe. I've used the commercial ones in the past, and they are awesome. I just can't justify their expense, so time for a DIY build!

[Cecil]

It made sense. Thanks for the info.

[kartlonbaugh]

My filter is very similar to the cyclone Davoponics drum filter. I believe that a narrow end of a conical drum will be better, but how to make a conical end of a cylinder and connect it to the problem of cheap and effective.

[keith_r]

i was looking for "pot scrubbies" at the hardware store to make a small filter, and found all natural hvac filters, "cut to fit", 1 filter was enough media to fill one 5 gallon bucket and cost about 4 bucks

[kellenw]

If I am thinking of the correct material, the HVAC filters will need to be replaced regularly, but they do work pretty well. Scrubbies will last basically forever, so are a better value over the long term. I've got scrubbies in use today that I began using in an Aquarium sump over 10 years ago.