Hello, I bought a used 90 gal saltwater reef tank. It has a 20 gal sump, I cleaned both tanks as best as I could but wasn't able to clean out the corner overflow that well. There is still a small amount of biological "stuff" down there...mossy seaweed looking stuff...it's only about 1/4 inch long and its down close to the bulkhead. I filled the tank and added new filter matterial. I have a filter sock attached to the down spout, the water then passes through a thick filter pad, then it travels thru bio balls, and then back up to the tank. I was wondering if its ok to begin cycling the tank. Is there anyone out there who has been in this situation? Is it safe to cycle a freshwater tank that was once a saltwater tank, that still contains a small amount of reef bio?

I don't have any experience with saltwater tanks so I can't help you. I looked online and found a lot of info but most is conflicting. This one makes the most sense and it's a site I use often. From what it says you'll need to get all the old stuff out first. Good luck and welcome to OFL !!

www.ehow.com/how_5535689_convert-water-fish-tank-fresh.html

After re-reading that I'm not so sure step #2 is completely right. I have fresh water tanks and I put salt in them when I do a cleaning. The others will answer too and make sure I'm right but I don't think some salt is gonna hurt them.

Thankyou for the advice and quick responce! I cleaned and flushed both tanks very well before filling and have also changed half the water. I really don't think there is any salt in either tank, if there was any salt left it should be pretty well diluted. I'll completely drain and refill the tank before set up, just concerned about the moss stuff in the overflow. I was hoping it would die in a freshwater enviroment. No such luck.

one good cleaning is enough, salt won't hurt the fresh water fish.
we normally apply salt during medication, thus, same principle applies.
the common concern is the scaled sediment accumulated in the glass...
wall which can be removed by using slice lemon on it, then rinse.
the acid in lemon help soften the scale and even if not rinse will
not harm the new occupant.

a picture will be appreciated by the members

btw, welcome aboard

I'm gonna try that! Thankyou very much, this web site is awsome, and everyone is so helpful!

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