Somewhat Odd Fishless Cycle

[Lenny_S]

I dosed 3 ppm ammonium chloride from Dr. Tim's into my 200 gallon system (160 gal DT & 40 gal in sump) 4 days ago. I waited 24 hours and verified I was at 3 ppm ammonia and then added 4 vials each of Prodibio BioDigest and BioOptim from their BioClean kit. So as of this post the bacteria has been in the system with 3 ppm of ammonia for 3 days. This morning I tested ammonia and nitrite and got 2 ppm ammonia and between .25 and .5o ppm nitrite. It just seems fast to me for a brand new tank with nothing but dry dead rock and dry sand.
My other water parameters are as follows...
Temp 78 degrees
Ca 400
Mg 1280
Alk 10.2 dKh
Salinity 1.026
PO4 = 0
NO3 = 0
pH = 8.1
I have 160 lbs of dry rock in the tank, 90 lbs of sand and I have 6 gallon containers of "rubble zone" in my fuge. I am not running anything else, no filter sock, skimmer is off, no carbon, GFO, etc... Flow through the sump is 5x tank volume per hour.
This is like any other tank I've setup over the years except for the fuge. I did a little experiment with the design. I'll start with a picture then explain...

The water from the tank flows over a baffle coming from the first chamber. It enters the fuge chamber at the bottom, but into a channel created by an under gravel filter that covers the entire 24"x15" area. This forces the water up through the rubble which provides a tremendous surface area of rock. Then it flows over another baffle at the other end to enter the third chamber where the return pump is. (Blue arrows show the water flow)
Could this be the difference? I'm not concerned really, but I'm very curious what Randy or others may think?

 

[jason2459]

Reversed under gravel filters are great. I've ran one for years and wont have a tank with out one. I have no idea what it does other then create a great area for various pods to reproduce like crazy. PaulB has a theory that it also traps detritus to give a good home for bacteria to go through the denitrification process. Could be but it also needs to be maintained as to much detritus will clog it all up. That would be my biggest worry with how you have yours setup with rock rubble compared to something like a dolomite or crushed coral substrate. Periodically the gravel needs blown out and get that detritus filtered out. I do it once or twice a year with a Diatom filter.

 

[Myka]

I don't like that you can't see how much detritus is trapped under there over time.

The cycle sounds about right to me. I would have used Prodibio Start Up though instead of BioDigest/Optim. It works better/faster than what you did. I don't think the rubble is making any difference yet.

 

[Lenny_S]

The BioClean combo packs were on sale. Actually this is my first time using the Prodibio product for a startup. I've used it to seed bio pellet reactors before in an established system, but not for a brand new tank. I still thought it would be at least a week or more likely 2 before I saw a dent in the ammonia. The only reason I tested it again today was because of another thread I was following on the Dr. Tim's ammonia dosing.

 

[Lenny_S]

Reversed under gravel filters are great. I've ran one for years and wont have a tank with out one. I have no idea what it does other then create a great area for various pods to reproduce like crazy. PaulB has a theory that it also traps detritus to give a good home for bacteria to go through the denitrification process. Could be but it also needs to be maintained as to much detritus will clog it all up. That would be my biggest worry with how you have yours setup with rock rubble compared to something like a dolomite or crushed coral substrate. Periodically the gravel needs blown out and get that detritus filtered out. I do it once or twice a year with a Diatom filter.

Yep, I was thinking about maintenance. I added acrylic strips to add another 3/8" of height all along the original under gravel to make it a total of 1" off the bottom, figured that gave me plenty of space for detritus buildup before it impeded the flow. Each high baffle wall has a cutout 1" above the normal running water level in case there is any blockage it will just bypass. I used the rubble because I can pull it out completely without a lot of effort and lift out the under gravel to "vacuum" out the chamber if there is ever a need for that deep a cleaning. And I can see at least the front inch or so of the bottom from the opening at the bottom of the baffle, it gives me a little sense of how much buildup there may be.
This was my first attempt at a reverse flow under gravel anything in a sump, but from other folks it seemed like a pretty good idea.

 

[Myka]

The BioClean combo packs were on sale. Actually this is my first time using the Prodibio product for a startup. I've used it to seed bio pellet reactors before in an established system, but not for a brand new tank. I still thought it would be at least a week or more likely 2 before I saw a dent in the ammonia. The only reason I tested it again today was because of another thread I was following on the Dr. Tim's ammonia dosing.

Nope, the bacteria in those products works very well. Experimentally, I've set up a 30-gallon tank with dry rock, added the Start Up product just on day one, and put 2 Clownfish juveniles in on day 3. Saw no ammonia at any point. I didn't add any ammonia besides the fish pooping.

 

[Lenny_S]

Nope, the bacteria in those products works very well. Experimentally, I've set up a 30-gallon tank with dry rock, added the Start Up product just on day one, and put 2 Clownfish juveniles in on day 3. Saw no ammonia at any point. I didn't add any ammonia besides the fish pooping.

Fantastic, mystery solved. I had no idea, thanks.

 

[Lenny_S]

Interesting update on my fish less cycle. I dosed the 3 ppm of ammonia like I said before. And this process intrigued me as I've never tried it before, so I took to testing ammonia, nitrite and nitrate daily. What I observed was from 3 ppm of ammonia I got a highest reading of 5 ppm nitrite as the ammonia hit 0. And from the 5 ppm of nitrite I got a highest nitrate reading of 8 ppm as the nitrite hit 0. So I observed there was about 1.5 times the nitrite concentration from the ammonia and about 1.5 times the nitrate from the nitrite
I find this interesting, does anyone have some thoughts?any

 

[Myka]

You're close, I think - maybe your nitrate is a tad high. I believe if you do the math, nitrite in ppm will be 2.7 times ammonia in ppm, and nitrate will be 1.35 times nitrite. So if you have 1 ppm ammonia, you will get 2.7 ppm nitrite, and 3.65 ppm nitrate. Keep in mind that the numbers you're getting could be some die off on the rock, even if you use dry rock.

 

[Randy Holmes-Farley Verified Community Expert]

As ammonia is oxidized to nitrate and then to nitrate, it picks up the weight of the added oxygen atoms to give the progression in weight above.

 

[Lenny_S]

Thanks Myka & Randy. This is the closest I've come to a "controlled" cycle. Still would not be able to tell what the overlap of the different bacteria would be, so this is not totally without some variables and unknowns. But it was interesting and I felt it was much more predictable than the cocktail shrimp or ghost feeding methods. And it was definitely quicker.

 

[Myka]

Thanks Myka & Randy. [..] And it was definitely quicker.

You're welcome. The speed was because of the addition of the bacteria and the ammonia. If you simply use dry rock, there will be ammonia come off most dry rocks, but it comes in the form of organics that need to break down into ammonia first, which usually takes a few days or more. Then you have to wait for the bacteria to start to colonize. So you did cut the time down by the process you used.