I am going to add some blackberries to my fermentor this weekend. at what rate should I add? I heard blueberries are 1 pound per gallon. is it the same with blackberries? I also realize it depends berryness I really want.
The general rule is one to two lbs of fruit per gallon. This is one beer where you may want to use a secondary a trimary because you may end up having problems with the seeds.
The beer is in a secondary now. I was going to siphon it into a tertiary (7 gallon bucket) and add fruit. I have just added flavorings in the past but always wanted to add real fruit.
I would put the fruit in secondary. No need to transfer that much – and you don’t want to put it in a… quadernary?? :o. Only a tertiary if there’s a bunch of fruit gunk you want gone. Less transferring beer=less chance of contamination issues and less work
+1. You should put the fruit in the secondary and then only siphon to a trimary (tertiary, whatever) only if you notice lots of seeds and chunks.
the secondary is a 6 gallon carboy isn’t that going to be a problem getting five pounds of fruit in there? I will need to put the blow off tube back on.
In that case, definitely rack to a bucket. Freeze/thaw the fruit first, then rack the beer on top of it. You might need to add some fresh yeast, depending on how long it’s already been in secondary. So after some time on the fruit in tertiary, you can rack to quaternary to help it clear. 
How much fruit to add depends on the base beer and how strong of a fruit presence you want, so if you gave us some style/strength details we can better suggest lbs/gallon.
It’s been in the secondary a week, I wasn’t thinking of adding more yeast
That’s fine, as long as you get renewed fermentation it’s no problem. I’d have a packet of dried yeast on hand though, so you’re ready to add yeast if you don’t see activity.
I was thinking of the yeast I started with (White Labs California) I always keep some dry yeast in stock. Thanks
instead of using a quaternary fermentor what if I used my keg as a quaternary so I could siphon of the trub from the bottom when I tap it. I would loose less beer that way.
Sure, that works. It might not be as clear if the keg is going to get moved around, but if it’s going to sit in one spot (like in a serving fridge) then it should clear up and be fine.
You could stretch a knee high nylon over your racking cane that will effectively strain all the floaters and sinkers from the fruit and go right from the secondary to the keg/bottling bucket. I do this when I dry hop or do fruit beers. Works wonderfully.