I put alum powder in my tank

[Diab2005]

I put alum in my tank instead of bicarb...what should I do???

 

[Essjay]

A huge water change to remove it all. Preferably all the water.

Since the cycle has finished, you do not need to add any more bicarb. That's just to stop the pH crashing during cycling. It contains sodium (the soda part of the name) and no soft water fish can cope with sodium long term.

 

[Diab2005]

I'm an idiot. Literally just finished the main water change my kh is like 2 so I read this was too low

 

[Essjay]

Because you have soft water, you'll need to keep soft water fish. With low KH you may find the pH drifting lower, but soft water fish are fine with this. If you search for posts by seangee you'll see that he uses all RO water for most of his tanks, and this has zero GH and zero KH. The pH in these tanks is very low but his soft water fish thrive in them.
During cycling, we want more bacteria to grow and they stop multiplying at very low pH. Once we have enough bacteria it doesn't matter if the pH drops.