DIY bio filters for large loads

[HoundsNTrout]

I've been raising trout for about 3 years now and got a question on the bio filters since I use what I call a semi recycled water system to save my well.
300G totes with anywhere from 300 to 1500 fish. Hatchery of sorts. I raise them from eggs to about 4 inches but sometimes I'll keep a batch going to 10 inches ( 100 or so of those in the tank, not 1500. )

50 to 75 Gallons are pumped out and refilled with fresh 2X daily.

Bio filers are 30 Gallon plastic totes above the tank filled with "lava rocks" and some whilffle balls with holes,etc.

Question on efficiency. Is it better to have a larger surface area with say only 6 inches of water or whatever? OR the plastic totes filled with river rocks?

In other words IS there any bacteria being developed in the lower and middle layers of my 18" high totes? or is most of it on the surface?

I"m starting to have some problems with nitrites mostly. Not sure if my filter is doing its capacity or I just need a better system. I have a pvc bar with holes running along the top of tote with outlet set to roughly the same outlet flow as the inflow.

So, in a nutshell would I be better off running a much larger surface area and less 'depth' ? or is my system fine must might need to be larger? Like 55G or something?


levels get to maybe .25 to .5 at times, but I use Seachem Prime and change water daily regardless. Sometimes I dont feed them for 48 hours and the levels return to zero but they gotta eat and grow so I go right back at feeding them.

I DO understand most "hatcheries" use a constant water flow but I get my eggs from a college who use the same system as I do. Their 2000 Gallon tanks have bio filters roughly 5 feet high X 3 feet in diameter.

Thanks. Sorry for the crazy long post. Just wanted to sort of tell ya what I was doing.

 

[markstrimaran]

Your lava totes will be bio active, all the way through.
A fluidizeds sand filter has the most bio area of any filter, 1 Cup of sand will support something like 20 pounds of fish. Your waffle balls are not giving you much surface area.

 

[HoundsNTrout]

Thanks. Yeah I figured on the wiffle balls. lol., I just tossed a few in there.

I think we gotta go up higher with the lava rocks I guess. IDK. I believe the nitrite bacteria is being out eaten by the ammonia ones is my 'feeling'.

Has anyone ever made their own fluidized sand filter? Filling with sand would be too compressed with minimal aeration seems, so how do those others work? Anyone know?

Because I am uncertain as to what is going on with mine other than competition between species of bacteria.

When cycled ( fishless ) in 55 degree water, when its done the tanks can handle 2 to 5ppm in less than 24 hours which is big. However the nitrites take 36 hours or so to disappear; but they do. When fish are added, it takes a few months ( fish might be 3 inches ) and the nitrites often come back, ammonia rarely.

So I guess that is my ultimate question. How to keep the nitrites to zero? More surface area or more "height" on the bio filter or both?

Its got me baffled since soon as you think you know the nitrogen cycle, try raising thousands of trout. LOL

 

[joe jaskot]

Too many fish, not enough filtration. With the cooler water temperatures your nitrifying bacteria slow down and cannot keep up with the waste produced by the fish. Exposing the bacteria to more oxygen would help, so more surface area would be better. Is there any way you could add some plants to your system? The plants would help to reduce the nitrite.

 

[HoundsNTrout]

Too many fish, not enough filtration. With the cooler water temperatures your nitrifying bacteria slow down and cannot keep up with the waste produced by the fish. Exposing the bacteria to more oxygen would help, so more surface area would be better. Is there any way you could add some plants to your system? The plants would help to reduce the nitrite.

I can try some plants and maybe a stone on the bottom of filters as well and see what happens. If not, I'll make my filters larger and make certain water is changed 2X daily. The hatchery where I buy eggs has way more fish per gallon than I do and only have a trickle system of new fresh water but their bio filters are quite large. I just contacted them to see exactly the size and media they are using per gallon and how many fish they have in each tank.
Other hatcheries that use no filters have constant flow, I will not do that here with my stream water because ya never know whats in the water. IT does seem like good water though, obviously you cant see fungus though.
Think I'll try the O2 bubbler/stone on bottom and see if theres any difference in a month's time first though.
But yes, i'm a hatchery and put tons of fish in the tank. But I know its possible so gonna keep trying things.
Thanks for all the info here.

 

[markstrimaran]

A sand filter is easy to build.
The bacteria break down waste as a team effort. Their are hetrotrophic bacteria that can hold real estate, but only if your water is very high in organics, more of a over stocked cichlid tank than a trout hatchery,
Bacteria activity at 55F is going to be about 10 timed slower than at 75f

 

[HoundsNTrout]

A sand filter is easy to build.
The bacteria break down waste as a team effort. Their are hetrotrophic bacteria that can hold real estate, but only if your water is very high in organics, more of a over stocked cichlid tank than a trout hatchery,
Bacteria activity at 55F is going to be about 10 timed slower than at 75f

Yes it is ..... SLOW.

Filters just can't keep up or it takes 36 hours for it to do so, that's the problem. I need to keep this many fish or its not 'worth' it.
When I see nitrites that's what I do, add Prime and feed the fish every 36 hours and also continue replenishing fresh water 2X daily. That works for 2 days. LOL

I"m always wondering if my media is good enough to allow oxygen to penetrate. Lava rocks seem to be a good choice. I have used regular smooth stones and they didn't work.

I'm adding an airstone to the bottom of one tote and see if it makes a difference. Have my doubts. Just because of the down pressure. Isn't that gonna impede the aeration effect of a stone on the bottom? IDK if that's even the 'problem". Maybe my filters are big enough.
2 feet X 18 inches X 18 inches filled maybe 3/4 full with the spray bar along the top going through 300G per hour in a 300G tank. Then I have 100micron sock filters hanging above tanks with pumps pumping I think 150G per hour. Along with a 2" X 10" air stones open wide. Oxygen in the water isn't a problem is always 8-9ppm.
Oxygen inside that tote might be different? But IDK. The way I have it designed with only 3 holes on top it really sprays well over the top and all media is submersed.

 

[HoundsNTrout]

Ok folks. Think I'm gonna try something larger. I'm going to use a 55G drum filled with lava rocks as media.
Question. Which might work best, a top spraying system water exiting bottom then back up a tube back into tank. ( drum is on ground not on top of IBC totes ).

OR water entering bottom of drum goes into a T sort of deal making water swirl, then media on top of this and water exits from the top back into tank?

Any benefits of either? THanks

 

[markstrimaran]

How many gallons of water.
How many pounds of fish.
What percentage of water is changed, and how often.

 

[HoundsNTrout]

How many gallons of water.
How many pounds of fish.
What percentage of water is changed, and how often.

300Gallons of water.

Anywhere from 25 pounds to 125 pounds of fish 300 Gallons.

25% water changes daily ( 12.5% 2X daily ) then it goes to 50% water changes daily. ( 25% 2X daily )



Also a side note or question. Pumping water in the bottom up a 55G drum is gonna require a hell of a lot more power eh? Meaning the downward pressure on a smaller pump?

THanks