1500g tank trouble cycling

[DrICJ]

Hello everyone,

I am having some issues getting my 1500g tanks to cycle. It was originally cycled freshwater and switched to saltwater about 6 weeks ago using Instant Ocean (not a reef system). The rapid change killed all the bacteria, so I had to restart the cycling process.

The system is set up with a large, aerated bioreactor, an ~200g sump, and a pressured bead filter system.

The ammonia dropped to practically 0 about 4 weeks ago, and the nitrites have been between 2 and 4. I add a large "sock" (pantyhose) filled with 35% protein feed to the sumps and leave them for 48 hours. When the nitrites are approximately 3 to 4 ppm, I remove the sock for a few days. The nitrates consistently read 30 to 40 ppm.

There are no animals in the tank, the temperature is 30 to 33 C and the pH is fairly consistent around 8.4. A few weeks back, I added Fritz Turbostart to one of the systems (I have 5 of them). Four of the systems are 1500g and one of them is 500g, and have seen next to no difference in the ones dosed than the others.

I have used filter media from another cycled system to each of the bioreactors (about a week ago), and have refreshed the media once during that week.

I have ordered the API saltwater kit, we have been using strips. I would say it is a problem with the strips, but the same container that reads 0 nitrites in another system reads 3-4ppm in the tanks of concern.

They have been cycling for 6 weeks with no change in nitrites or nitrates unless we do a water exchange.

Thanks in advance.

[54seaweed]

yes saltwater will kill freshwater bacteria as it is different , first remember you need about a lb of rock per gal . best way to start is with a few deli shrimp in a sock or stocking this will start your ammonia source quicker, remember be patient as your tank is large it may take longer to cycle than a average size tank,


this link should help you get started up
Cycle your salt tank - Aquarium Advice

[DrICJ]

There shouldn't be a difference in using decomposing shrimp as a nitrogen source vs using half a pound of 35% protein feed and replacing it on a regular cycle.

I am wondering how long it takes for the average size tank (lets say 100g) to cycle once a significant level of ammonia is introduced.

Also, what does the rock do? These systems do not have rocks. As a matter of fact, I cannot put rocks into them and still have them serve my purpose.

Thank you

[bribo12]

Just curious what are they going to be used for if you aren’t putting live rock in them? That’s a pretty common theme with marine tanks as it provides the main source of surface area for bacteria growth and filtration

[DrICJ]

These tanks are not for decoration. They are experimental systems that I am growing animals in. My animals always wind up fat and happy. I have just never had to mix my own saltwater before, it has always been pumped in from a natural body of water.

[Brookster123]

Question for the crowd. Could an undergravel filter be used with a crushed coral/live rock rubble bed in replacement of stacked rock?

[bribo12]

Originally Posted by DrICJ

These tanks are not for decoration. They are experimental systems that I am growing animals in. My animals always wind up fat and happy. I have just never had to mix my own saltwater before, it has always been pumped in from a natural body of water.

Gotcha I was just curious.

[54seaweed]

very good question brook . I never even thought under gravel as they are so obsolete in the SW hobby . we would need to wait on someone from that era lol to give us that answer .


since you want no rock in the main tank you could build a large sump with no baffles fill that with rock and that will hold and serve as your bio load

[Andy Sager]

I would wait until you get the more reliable test kit for readings as the strips may be giving you false readings. That said:
If your ammonia has naturally lowered and nitrites are present, your bacteria bed in your reactor has started. The nitrate level being there at all would assume that the second stage of the biological filtering is happening making the current test results from the strips suspect. ( Unless the nitrate levels are coming from your source water.)
Assuming all is correct with the tests, the temp is a bit high for optimal biological growth so if you can lower it to closer to 25C - 29C, that will help increase biological growth rates. Next is your reactors, you may need to lower the flow rate to allow more time for your water to be filtered. The way to know is to test water going into the reactor and water at the outflow of the reactor. If there is no change, it means the water is flowing too fast for anything to happen. Also, what is inside the reactors for biological growth to adhere to?
As for using rock, it's nothing more than a different source of nitrifying bacteria and is not a "necessity" to create a bacteria bed. Depending on how your reactor is set up, it should be serving the same purpose of the live rock.

Hope this helps