Moving fish from high to low nitrates?

[Spiegel99]

Not sure what to do in this situation. I need access to a wall behind my 45 gal tank asap because of a plumbing issue, and have decided to just move all my fish into a new 75 gal tank since the 45 is too difficult to move even when mostly emptied. The 75 gal has been set up for about 3 weeks now, most of the water parameters are where they should be except the nitrates, they're staying at 0ppm. I can't get the nitrates to go up even after adding moss and water from a sponge filter from the old tank, and a couple new fish. The nitrates in the old tank are a bit high at around 40-60ppm.

I need to move my fish as soon as I can, but I'm afraid the drop in nitrates would shock them. I plan to do daily water changes, but I worry that would take too long, because obviously the longer I wait the worse the plumbing issue will get.

So do I just do water changes for a week and see where that gets the nitrates in the old tank, is there some way I can quickly raise the levels in the new tank, or do I just very slowly acclimate the fish to the new water before adding them and hope for the best?

[Aiken Drum]

2 ways to do this.

Either take as much water as you can from your old tank, move the fish over, and then refill the new tank with clean water. That would be like a 50% water change. I regularly do this and never had an issue.

Or spend some time doing 50% water changes in your old tank, gradually bring the water down to near 0ppm nitrate in the old tank and then move them to what will be similar water conditions in the new tank.

Really moving fish from 40/ 60ppm down to zero probably wont be an issue. Its when you are dropping from 100s you get issues. But to play safe no reason to not go with either option 1 or 2.

Your new tank isnt cycled. As you are seeing zero nitrate im assuming you havent been dosing ammonia over those 3 weeks. You will likely see elevated ammonia and nitrite shortly after you add fish.Do you know how to cycle your tank?

[Spiegel99]

Thank you for the suggestions!

It's good to know that moving them from 40ppm to 0 wouldn't cause many problems, but I would feel better if the levels were lower before moving them just in case. So, I think I'll try doing the 50% water changes starting today, and see where the nitrates are at by the end of the week.

I cycled my 45 gal when I first got it but that was years ago, so it didn't quite remember all of the steps. I know I probably should have looked it up, but I was in such a rush to move them that I didn't really think about it :/ I'll watch for the ammonia and nitrites to spike and go back down, then check the nitrates again before moving the fish.

[Aiken Drum]

It typically takes 6 to 8 weeks to cycle a tank before you add fish. Often longer. Ammonia can only spike if you are adding ammonia. Are you adding an ammonia source?

You can cycle a tank with fish, but the more fish you stock into an uncycled tank the more hazardous for the fish that will be.

[Aiken Drum]

To add to this. When you move the fish to the new tank, can you move the filter from the 45g with them? The filter will already be cycled, and running your old filter alongside the new filter for a month or so will give your new filter chance to establish a beneficial bacteria colony and get cycled before you then remove the old filter.