Live rock is an essential part of a reef tank, once “live” it becomes the main biological filtration in the aquarium. It hosts aerobic and anaerobic nitrifying bacteria required for the nitrogen cycle that processes waste, along with providing your fish & inverts with somewhere to hide and somewhere for your corals to grow on.
Always on the hunt for a bargain, when I first decided I was going to dip my toe into the marine world I came across someone selling “live rock” not too far away from me at a very reasonable £1.00 per kg. Obviously, I snapped it up, brought it home and stowed it away until it was needed.
It is getting to the point where it will be needed. I have just ordered an RO/Di unit and will soon be able to make my first batch of salt water to start curing my bargain rock, so I pulled out some of it to start taking a closer look at it. There are some lovely bits of rock in there, with some lovely shapes and unusual swim-throughs.
With nearly 6 weeks of buying nothing further for the tank and just doing nothing but research, my mistake hit me as soon as I looked at the rock. I’ve bought ocean rock (also known as holey rock or texas holey rock). In my defense, I was an excited newbie who bought rock that was advertised as “live marine rock”.
Ocean rock is not as porous as live rock, it is a densely packed limestone that is removed from the ground rather than the sea. From what I understand it was once live rock, but over a ridiculous amount of years, it has been turned to limestone due to compacting pressure. Ocean rock is more commonly found in cichlid tanks.
Panic set in & I started looking into how bad my mistake was or if I could use ocean rock in my saltwater aquarium.
After about a week’s worth of research time, I have decided it is not that bad and I am still going to use the ocean rock in my tank. It turns out lots of people use it as a base rock to save on cost and very few have experienced issues with it. I even posted the question on a Facebook group and I didn’t get a single negative review of holey ocean rock.
I do have about one-third of the rock that is true live rock, and to compensate for the lack of live rock in the tank I am going to put several blocks of MarinePure in the sump. The ocean rock will eventually become live, but it will take longer and it will only be the surface of the rock that becomes live. It will also lose the bright white colouring, but again, it will take longer.
I already have more than enough rock for my display tank. With the ocean rock & the live rock truthfully it would probably be enough for filtration on the tank, but just to be safe, I think the MarinePure will just give me that bit of an extra buffer and allow me to not worry myself over it.
If anything is going to leach from the rock it is likely to be calcium, which should help my corals once they are in the tank. Some people o report a slight rise in pH using this rock, but it is minimal.
Overall, the cost of live rock is limiting the amount I can have in this tank. I feel I have read up enough on the subject to be comfortable in saying that I a happy to use the ocean rock on the condition I can get a good amount of MarinePure or live rock rubble in the sump.