FW tank into a BW tank

[Jase]

If I convert one of my FW tanks into a BW tank using my current BW stuff to cycle, will there be a mini cycle as the FW bacteria dies, or will it go smooth?

[Iliveinazoo]

What is your current BW stuff?

Is there anything in your FW tank at the moment?

[Jase]

It's a 30g FW community tank. small fish, not a huge bio load, HOB AC filter. BW is 20g but basically the same (slightly larger bio-load) with an SG of 1.010

[edit]
The BW "stuff" would be filter, substrate, decor, the works.

[Iliveinazoo]

You're freshwater fish will not be able to cope with the salt water.

Most of the existing brackish water bacteria on the substrate, filter and decor will die off when moved from SG 1.010 into the freshwater, but i presume that some will survive which will reduce the cycle time, but the tank will still go through a cycling period.

What i think that you are doing is either:
1. Completely stripping down your freshwater tank and creating a whole new look with new substrate, decor and fish.
or
2. You are happy with how your FW tank looks and want to up the salinity to match your other Brackish Water tank.

1. Stripping down means that you will have to go through a definate cycling period although the time will be reduced as you will be using mature filter media, substrate, decor.

2. Depends on the fish that you want to keep and at what salinity. If you going low salinity then you could up your tank water by 1.002 and stick some bumblee gobies in straight away and bring the water up by 1.002 on the next water change and you're there, however if you are eventually going higher and will be keping mid - high slainity fish then this is what i suggest:
Carry out water changes every 3 or 4 days and include salt with your new water. Other people on this forum suggest that you do not increase the salinity of the tank by more than 1.002 each water change. the problem that you have in doing this is keeping a source of ammonia in your tank because if you've removed the fish then you've removed the ammonia and ultimately the bacteria's food source (you will need an ammonia source). If you have amano shrimp or another brackish water animal in your freshwater setup at the moment then i would leave them in and they will provide the ammonia for you (remove the animal at it's maximum salinity level and take care to acclimitise it back to freshwater if you are putting it back into a freshwater tank). If you are planning on keeping a mollie then that is great because they tolerate fresh to marine water.

I hope that this makes sense - i've rushed it slightly because i'm about to go and play 5-a-side

[Jase]

well I see you put some thought into that, which I appreciate. however I think we are on different wave lengths here.

I'm going to take all my FW fish and put them in a separate well established FW tank. then take all the water out of the FW tank. then fill it with everything in my brackish tank and top it off with water of the same Sg. also puting my well established filter on the "new" BW tank. I want to know if this will go smooth, or if I will have a huge spike from the dieing FW bacteria left over in the tank.
or can it all be prevented by cleaning my filter and substrate...?

please give me a little credit, I like to think I know a good bit about aquariums and fish keeping. this particular move has me questioning the outcome though.

[edmlfc1]

If you are moving everything from one tank to another, just rise out the tank once it's empty and I don't see any problem. I went from a 44 gallon to a 125 gallon. I also added a new filter, and used the filter that was on the 44. I had a mini cycle that lasted 2-3 days but not a big deal.

[Jase]

ok, I'm just going to wash the FW substrate and get new filter media for the FW filter.

now I'll go off somewhere else for having started a pointless thread and causing confusion.