SW question

[Ice]

I was reading The Conscienctious Aquarist and on p.128 under Every 6 - 12 months maintenance, Clean & Replace Substrate. It says it's recommended to replace some of the faster-disolving substrates, particularly coral sand or gravel. Are they talking about Arag-Alive sand ? Do any of you replace substrates ?
Also on p.107 of same book, Step 14 : Inoculate your System,: It recommends to add the all-essential bacterial cultures to the aquarium. It also states to start with a cup or two (a pound or 2) of gravel or live sand from a healthy, long-established marine aquarium. It more so "seeds" the beneficial microbes in the tank. Is this a common method ? Or simply adding activated carbon is more a common method preferred ? What would be the best way to do this in that step ? Great book yet kind of got to read and re-read each section again to gain the knowledge & understanding.

[harif87]

The reason why you add the sand from an already matured tank is because it has the neccessary bacteria and living organisims to keep your tank clean and ammonia free. By adding the Live Sand or Live Rock you pretty much skipping the month and a half long cycling process since your taking the bacteria from somewhere instead of growing them yourself. But depending on how much live sand you add it will determine how much of a load you can put on your bio filter at the start of your tanks beggining. The bacteria in the sample of sand or rock then reproduces and populates your tank making it able to handle the full bioload of the [not over-stocked] tank. Carbon on the other hand cant replace the need for the culture of living bacteria since carbon wont nitrify ammonia or nitrite. Some people might argue that carbon can take the place of a protein skimmer since it can take out DOC's from the water, but it is not considered to be a substitute for a bio filter.

Dont know much about the dissolving sand, might be a thing to look into though....

[Damon]

It doesn't dissolve that fast, if at all. If you keep up with waterchanges, you replacing the calcium that is being depleted. If the tank stays close to saturation then you shouldn't have to worry. I know people who have never changed sand and the tank is going for years now.

[Osiris]

Basically i was under impression the calcium will dissolve but only if the ph drops to raise ph cuz at a certain level a chemical reaction happens in the substrate that then releases that to stablize ph levels....but like he said like its ever needed cuz when u mix salt, it contains calcium and buffers to raise ph to where it needs to be.

[Reefneck]

Agreed. I have never seen anyone replace their substrate unless they were changing tanks, moving or just changing out the type of substrate.

Activated Carbon is Not really a good idea in saltwater tanks. It actually can cause some serious health problems for fish. I've not seen it often, More rarely but it can happen.

[Ice]

So what you're saying it is a good idea to add a pound or 2 from a healthy long established tank then. As far as live sand goes, it is still a good idea to do a partial live sand change every 6 - 12 months ? Would a refugium a better option to keep the sand from losing its beneficial established microbes ? That will be another topic a little later today to ask.

[Fishfirst]

I think what Fenner is trying to get here is that you should every once in a while take part of your sand and replace it so you don't get so much detritus build up... fortunately if you have a good sandbed of live critters, most of that detritus is used and eaten up. If you want to practice replacing the sand bed at a slow rate (maybe 2-3lbs every 6 months) thats fine... just remember that other new reefers might want what your disguarding.

[TheOldSalt]

Aragonite does slowly dissolve under aquarium conditions, but the process is slow and subject to a lot of variables. Many of these variables are a byproduct of confinement in an aquarium, which is why it's such a factor in a tank but not so much in the wild.
Other calcareous rocks also dissolve, but the oolitic size & shape of aragonite sand provides it with massive surface area exposed to water, thusly dissolving it faster. This is not the only reason aragonite is preferred over the other types. The shape of the calcium molecule found in aragonite makes it much more immediately bioavailable than other types of calcium.
The dissolving is of course why we even want the stuff in the first place. This is what makes aragonite so useful as a buffer and source of calcium/magnesium.

So why change some of it every six months?

Well, it's not really a matter of it being used up, but of being covered up... with bioslime. Over time big sections of your sandbed will become clogged and choked with various stuff which pretty much keeps it out of direct contact with the water in any meaningful way, and this in turn has an effect on the environment immediately surrounding the sand which allows for an undesirable trend of pH/alk decline among other things.
There are certainly ways around this, such as keeping the sand well-stirred or even using it in a reactor, but as already mentioned above, most people never really have any problems with this at all on account of making up for it with their other normal maintenance and dosing. Bob Fenner is simply telling you the perfect-world solution to the problem which will indeed give you superior results over not doing it. So, then, you can either not do it and do just fine, or do it and do even better. You can choose between higher maintenace but less sand changing, or lower maintenance and more sand changing. Sand changing gives you fresh minerals ( lots more elements locked up in aragonite than just calcium, you know...try about 80 of them ) coming at you at an increased rate, which gives your whole system a boost and saves you some bother with manually measuring and dosing all the time. ( again, a reactor helps a lot with this, but isn't crucial )

I've tried it both ways, and while I can say the sand-changing is worth the trouble for many applications, it isn't always worth it. I would do it if I were keeping a tank full of really demanding corals or if I needed to ensure a constant good crop of food organisms worth feeding to the fish, but otherwise I probably wouldn't. I'd tend toward and ecosystem filter in either case, by the way, but that's another thread.

Oh, as for innoculating your tank from an established one... that'll work okay if you absolutely have to, but there's hardly any real reason to have to. Just buy your sand & rock directly from the Florida rock & sand farms and have to shipped to you overnight. You'll get vastly superior product than anything you'll be apt to find in most petshops, and your tank will be instantly ready for fish the very next day, with bacteria, amphipods, snails.. the works. The price would be about the same, but the fresh stuff still has everything in it you want.

[Ice]

Well, that certainly clears that up for me ! Thanks Old Salt !