Questions about live rock
 

Hello all,

Thanks for all the info collected here. Its been great to lurk and learn.
So, I'm thinking about converting my (now empty. It's former inhabitants went into a 55g) 37 gallon tank to saltwater. I was at my lfs today and asked about lace rock. The employees there eagerly proceeded to show me this rather large piece they have. They said that they got it from a guy who broke down his tank and, because of its size and shape, they have not been able to sell it. The piece is around 2 1/2 - 3ft long, about 9in tall and close to 50lbs. Right now it is in the tank with all the other live rock. This thing is completely covered with coralline algae and such, so I cannot see the actual surface of the rock. The other thing is that the rock is literally shaped like a wave. It looks really cool to me, although, it may not be the ideal shape. I've attached a very crude (sorry) drawing of what the thing looks like. Unfortunately I didn't think to ask y'all, let alone take a pic or two till I was half way home. The kicker is that they offered it to me for $20...I'm thinking I could/would break this up to make a more suitable formation. So, I have some questions:

1. Seeing the "drawing" and knowing that this thing looks pretty much solid, would this be enough to adequately filter the tank? I asked them and they wouldn't say yes or no, just that it wouldn't provide as much filtration since it isn't so porous like many other rocks. (I would be breaking some of it up to do some scaping, making caves, shelves, etc..). Although, who knows, it could be holey, just plugged up with growth?

2. I know lace rock doesn't contribute to buffer the ph, would it be sufficient to go with crushed coral for substrate (out of the tap: ph 7 and very soft water of 0-1 and average 30-40ppm)? If so, how much would you recommend, more than the general +/- 2in (assuming the substrate would be the only buffer)?

3. Being that this piece is very well established "from head to toe", would it be necessary to clean and cure it for a fresh start or could it be used straight away? I've seen mixed thoughts on this and even the lfs guy didn't answer in favor of one or the other. He just listed some pros and cons of each.

Oh, and if it matters, I'll be looking at FOWLR, for a long while, at least.

I have more questions but this post is too long already.

Thank you ahead of time for any info,

Will

1. It's hard to be sure but I suspect it would provide enough surface area for the bacteria. The big question is does the rock have a lot of absorbed phosphates in it. If so once you set up the tank you may need to use a lot of GFO in a reactor to remove it.
2. Your rock and sand should never act as a buffer, if your pH were to ever drop low enough for either to have any effect at all on the system there would already be a major die off. Crushed coral is not a good choice for a marine tank, it traps way too much detritus which will lead to high nitrates and algae issues.
3. It's hard to predict if the rock is fully cycled or not (if by "ready to use" you mean cycled). The quickest way to find out is to add enough pure ammonia without surfactants to raise your ammonia level to 2ppm. If the rock is fully cycled the ammonia will drop back to zero in 24 hours, if not simply wait for the ammonia and nitrites to drop to zero and then you are good to add livestock.

Thank you for your reply.

1. That is a good point about the phosphates and I suppose I wouldn't know unless I got it home and in my tank.

2. As for the substrate, I have seen a few places which listed crushed coral as an option and I know we sometimes use it in the FW world to buffer hardness and increase ph. I just assumed that it would be the same way with SW, wrongly, lol.

So, how do folks go about raising ph for saltwater? I saw it suggested that some saltmixes will do this, checked a few of the "best sellers", but I didn't see anything on it.

3. Thx for the info. Yes, from what they say, the rock has been in a mature tank for a long while and should itself be fully cycled (and that would be a great way to tell). But, I was more asking if people would suggest leaving it out in the sun for a few days, then beginning to cure it all over again or if they would try to stick it in the tank straight away? The purpose of buying live rock over dry rock is to skip part of the process, right? I'm just a little concerned about unknown hitchhikers.

Thank you again,

Will