Testing DT for ich

[GoTRiCe19]

So my tank has been fallow for 4 weeks now. I have all my fish in qt. no signs of ich for 2 weeks. Now my question is after hypo and my DT and qt is the same salinity i want to test my DT for ich by either placing a 3-5 pound live rock from the DT or changing my qt water with water from my DT. If ich shows up in qt after I know fish in qt should be ich free that means dt is has ich. And in my qt I can rid ich in 2 weeks and try again.

Reason I want to try this is that even after 8-12 weeks fallow I seen ich come back.
I'm going to wait it out another 6 weeks but what is the harm in infecting my qt to test if ich is in my display. Anyone have any other tips on testing dt for ich?

[sleepydoc]

Unfortunately I know of no reliable tests for the presence of ich. There are several problems with your proposed test/course of action, however.

First, the recommended fallow time is 10-11 weeks, depending on who you talk to. Since you're only at 4 weeks, one wouldn't necessarily expect your DT to be ich-free. Now, assuming it's not, taking some water and/or rock may or may not transfer parasites into the QT which may or may not infect your fish which may or may not actually show overt symptoms of ich, so even if there was ich in your DT, you wouldn't necessarily see signs of it.

You say you've seen ich come back after 8-12 weeks fallow; that's a wide range. 8 weeks is significantly less than the recommended time, but 12 weeks should be good. If you saw ich come back after 12 weeks, I would suspect it either wasn't totally eradicated from the fish and was simply re-introduced with the fish, or there was some cross-contamination between the QT and DT during that time.

Also, you mention that you're using hypo - IME, hypo is difficult to perform correctly and method failures (such as a slightly miscalibrated refractometer) can lead to reintroduction to the DT as mentioned above. Also, there are reports of hypo-resistant strains of ich, which would also lead to a treatment failure.

[MellowReefer]

+1

Ich is most likely not present on all rocks, so you couldn't test if it's still in there by using only one rock. Really no way to know for sure other than waiting.

I agree with the above post, there are too many cases of hypo not curing the fish, although it may reduce it enough for you to think they are cured and then it comes back later. If I were you I'd use cupramine or tank transfer this time (depending on your fish's tolerance of copper) and continue to leave the DT fallow for the full 10 weeks.