lduncan

Finally they came up with a decent flexible mounting system!

Which part?

God damn it. That edit function strikes again. That should read "For me sand doesn't seem to be the answer to the feeding question."

Remember it's not the ONLY way they get their requirements. That planktonic food isn't always there, it comes in goes in cycles. Corals either have to be good at storing stuff, or they need to be able to get from other sources when plankton aren't available. It may happen that in Nature corals get the majority of their no zooxanthellae provided food from plankton, but that doesn't mean it has to get it using this method in out tanks. The other sources may be more convenient and easier for them. That pretty much sums it up. For me sand does seem to be the answer to the feeding question. Layton

Less available. Didn't forget that. Critters are critters, big or small. They are not as top notch as the bacterial coral food that they just ate. Plus the coral has to use more energy to digest it. So it's a double hit. Maybe a recap: But they have also taken their slice out of it. They don't crap exactly what they ate, there is a reduction there. Layton

Screwed that up. Need that edit back.

And Oh - Layton you got enough marbles to know I didn't forget that! :lol: . Photosynthesis? Do you realise that when farmers grow a crop, they put fertilizer on it? Like all photosynthetic organisms, the crop require a balance of minerals, trace elements, etc. Nitrogen alone will not cut the mustard. So do zooxanthellae need all that. How do they get it? It is ingested by the coral. That is what symbiosis is all about. So what happens if the farmer does not see to it that the crop has enough of the required nutrients? Stunted, ratty crop. Bit like some of our corals.

Does anyone else find this a weird conclusion from Dr Ron?

I thought I explained that. Food (bacterial detritus) drops into it from above. Critters are able to reproduce in the safer confines of the sand. They feed on this bacterial detritus, producing an organism of lower nutritional value which itself produces waste, but it doesn't create more waste than previously eaten, it's not possible. Then it may or may not be possible for corals to eat some of these critters which reduces the availability even further. Corals are good at digesting bacteria, so good that researchers had trouble determining whether they do in fact eat them, as the time from collection to doing a gut analysis was long enough that the bacteria was unrecognisable (sometimes only several minutes), all they could find were partially digested pod shells. The thing is that by actively encouraging other critters to feed on bacteria, you are reducing this proportion of highly nutritious coral food. Sure the sand bed supports bacteria, but it can't possible create more bacteria than the food your putting in allows. You put so much food into a tank, and say (just to keep things simple) it goes to either bacteria or critters. BB you have a lower critter populations, which means more of that food is going to end up being associated with bacteria which is an easy food source for corals. You put the same amount of food into a tank with sand, which has a high critter population so proportionally less of that food is going to be available to corals as high nutrition bacterial coral food, while the rest goes to supporting the critter populations, which may or may not be the right size and type. It's not always the point. Depends how you want to run it. But if that's what your saying, then you're supporting my claim that BB has more food available to corals. For a skimmer to work, it requires the stuff to be floating in the water. If a skimmer is removing more in a certain period of time, that means there is a higher concentration of food in the water. If the same skimmer is not removing as much in a certain period of time, it means that there is a lower concentration of food in the water. If putting sand in a tank reduces the skimmer output, doesn't that imply that it also reduces the available food in the tank? Isn't the idea to have a high concentration of food available in the water so corals have access to it? :-? I've read that a couple of times I still don't see what you mean? Layton

Isn't that interesting. It's that what everyone goes to a lot of effort to avoid? Brown corals. Doesn't that show how much dissolved nitrogen is available in tanks, and how difficult it can be to keep it low enough? Maybe it does provide a significant source of nitrogen, even in the cleanest of tanks? The question is how low is low nutrients? Is it possible to reduce dissolved inorganic nitrogen in our tanks to a level where it can't provide a significant source for corals? Layton

The wide variety of different corals that there are, have an equally wide spectrum of nutritional requirements, even within genus. The also have a variety of methods they can use to get these nutrients. Different environments go through cycles of varying length and at different times are in different state which may allow them to support corals which they may not at other points in their cycles. You have upwellings at the reefs edge which are cyclic, providing sources of organic nutrients, then in periods of no upwellings you find the water higher in dissolved inorganic sources. Corals need to have a variety of sources for their nutrition, to cope with these cycles. Just because they use one predominantly in a particular natural environment, doesn't mean it has to use it in our tanks, it may be easier or more convenient ways available. Layton

What does it matter if it never leaves the sand bed and gets to where it's needed? If it's nutritional value is diluted, and takes more energy for corals to digest? Not to mention corals don't just feed on any critters. And some corals are less able to catch and hold onto all these critters than others. So what about inorganic sources? Corals use these as well. They are abundant in our tanks. Layton

I didn't say the sand bed isn't producing anything useful. I'm saying it's taking a portion of the MOST useful stuff, and converting it to stuff which is not AS useful (lower nutritional value and harder to digest). It also makes less food available by trapping it. Removing it from the water column. It has to be in the water for corals to have a chance of getting it. Are you saying that a BB tank exports more than a tank with sand, given same food input and same skimmer? Well they don't produce any extra food. They convert existing food to different types of food. It's not the surface that promotes the growth of bacteria, it's the conditions they are in. Bacteria live in broths, they aren't necessarily attracted to inert sufaces because of some need to hold on to something. Some go to the effort to create their own broths in environments which are otherwise hostile. Sometimes the broth exists already. The reason why bio-balls and sand beds attract large bacterial populations is because they mechanically trap and therefore concentrate the very food which bacteria feed off. What if the food is never trapped on a surface? Well the bacteria don't care, it's all about the food and environment to them. They'll happily float around with their food. Here's something from Eric on bacteria: Also, there has been a lot of focus on organic food sources. What about inorganic sources like ammonia, nitrate etc. These are not exactly in short supply in our tanks. Couldn't they be considered a large source for corals? Layton

Not confused at all. Don't forget that zoxanthellae are pretty much plants -> photosynthesis. Coral tissue is animal cell. They don't photosynthesise.

What matters is the amount of food in the water column, after all that's the only place the corals can get it from. Anything in the sand doesn't count they can't get it when it's there. So two tanks, one with sand, one without, exactly the same skimmers etc. Now imagine if both had the same mass of food floating in the water column (same amount of food in the water available for corals). The skimmer is going to remove a similar amount is it not? Even though there may be a lot tied up in the sand, that portion is irrelevant, they can't get it. Food has to be suspended for corals to get it, if it's suspended the skimmer can get it too. See above, same food concentration, same skimmer output. What does it matter if it can hold the stuff. If it's holding it, the corals can't get it, so what's the point in having it there? Layton

Ok here's what I find wierd. First he says that bacteria are better than pods for providing nutrients. Bigger bang for your buck. Then he says that detritus is a good food source for this bacteria to colonise. He then goes on to say that sand dwelling creature are a big competitor to corals for this nutrients: But then goes on to promote the use of sand as a food source: To me that's just a weird conclusion. Using something which actually eats one of the most nutritious forms of food for corals (bacteria), and converts much of it into a form which is harder for corals to digest, and provide less nutrition. Seems kind of backwards to me. Surely you want the food which is in you tank to be easy for corals to digest and nutritious? The habitat sand provides does the opposite, by Ron's own writing. Layton

Wasp that's all irrelevant. How about a question relating to what I posted. What don't you agree with? Layton

Your right, I have no formal qualifications in marine biology. However, I can read what others write, as far as scientific findings go, then form my own conclusions on that. However, to dismiss any conclusions I may have come to based on the information available, you have to come up with reasons why they don't hold up. Not having the relevant formal qualifications is not a valid reason. The second question. Dr Ron can answer that: The waste is already in a form which is edible to corals, coated in bacteria before it gets to the sand. It's that sand which dilutes it and makes it LESS useful, by packaging it up in the form of pods, which are required to leave the nutrient rich environment of the sand, into the water column, where some corals may be able to catch them, if they are the appropriate size, not too strong, and if they do manage to hold on to them, they have to spend more energy digesting, than bacterial detritus. The fact is the sand doesn't just produce bacteria out of nowhere, ultimately the vast majority the food in the system comes from YOU putting it in there. In otherwise identical setups (matching imports and exports), a BB tank will have the same amount of food as a tank with sand. Only in the BB tank, there is more of it in a more digestible form for corals. People forget that for detritus to get to the skimmer, it must have been floating in the water column, which means corals had at least some opportunity to grab it. If it's not in the water column, how are they supposed to get it? Also the idea of BB is all about control, you have complete control over the system.

Did you get standard float prices as well? Or are you going to do the whole thing in low iron? Layton

Started a new thread about feeding here http://www.fnzas.org.nz/fishroom/viewto ... 206#155206 Pretty much sums up my opinion on the matter re sand / no sand and feeding tanks. Layton

All this talk of feeding pretty much comes down to where corals get their nitrogen. So what can corals feed on to get this nitrogen? Dissolved inorganic nitrogen(Ammonia nitrate etc.), bacteria, microplankton. Starting from the start how do these nutrients enter the tank? Well the bulk of it is going to come from you putting it in there. Once the food is in there, what happens to it? Much of it is eaten by fish and animals in the tank. Some of it may be skimmed out. Some may get trapped in crevices and be broken down by bacteria. All animals produce waste. So once the fish digest the food they produce ammonia and crap, esentially detritus. Now say you have two identical tanks, one with sand, one without sand, and you feed them equally. Logically, the mass of nutrients in the tank is going to be the same. What some people seem to be saying is that the tank with the sand somehow has more food available, and somehow is more benifical to corals? How can this be? It's impossible, unless the sand is magically creating matter. Adding calcium carbonate to the bottom of the tank does not increase the ammount of food available to corals. In fact it may result in the opposite. Getting back to detritus created by both rocks, fish crap, coral mucus and other animal waste. This stuff is basically bacteria a collection of bacteria. Corals actively farm bacteria in their mucus for their own consumption, and bacteria in general are a good food (nitrogen) source for corals. This is interesting from Dr Ron: What would happen if you didn't have sand, and could keep this stuff in suspension and not let it settle? Wouldn't it stay in circulation in the water column available for the corals to feed on? What happens when this detritus get stuck in the sand? It prodvides a rich habitat for critters, pods etc. What do they feed on? The same bacteria ladened detritus which has come from the rocks, fish and corals. So so far there is no magical increase in mass of food in the tank. So far, all the sand be has done is remove some of it from general circulation in the tank. Corals can't get that portion of it now. So now in the sand with all those different types and sizes of pods, worms, algae, and snails, you somehow need to get those to the corals? You will get a bunch of them venturing out at night and get consumed by corals (assumung they are the right size for the coral, aren't too strong, and the coral actually digests them etc) Now looking at the BB system for a minute. There is still the same amount of food in the system, but it exists as free floating bacterial infested detrital particulates. You don't have any sand to hold it, and you don't have massive algae, pod, worm, and snail populations to consume it and make it less available to the corals. Sand beds can be considered an animal in themselves, and compete with corals for food. So in virtually identical tanks which are fed the same amount, which one has more food available to the corals? One where it's at the bottom tied up in sand and critters, or the other tank which is floating free in the water as bacteria ladened detritus? Also, remember that bacteria, weight for weight, are more nutritious than other critters like pods. Your looking at 10% in undeigestable shell, a lot of empty space, and also require a lot more energy to digest than bacteria. Sand beds actively try to convert bacterial mass, into critter mass. Surely this just makes life harder for corals? Some more stuff from Dr Ron: He just seems to come to some weird conclusions. Why does he promote sand beds so much? (Financial interest maybe? His love of critters maybe?) His own writings suggest they're not all their craked up to be. I didn't even touch the other things which sand beds do. Personally, I'll only ever use sand for aesthetic reasons. It's not a nutrient remover, nor a food creator. They just cycle and change stuff. Often not for the better. Layton

Also Cookie, it is true that some corals can get up to 98% of their food from zooxanthellae alone. Of course there is a whole spectrum of requirements for different corals. This number also seems reasonable, as zooxanthellae are more associated with supplying nutrients for calcification. Where as the "captured" food is used for supporting the coral tissue itself. When you look at some sps, they lay down a LOT of calcium carboante skeleton mass, relative to their own cellular tissue mass. They are just a thin coating over the skeleton. Layton

It's not mincing words Cookie. I've never said corals only need light to live, not even SPS. Just note that there is a difference between nutrient poor, and food poor. In the context we usually use these terms in the hobby. The older "Berlin" systems are not the same as BB systems of today. They had problems because of other factors, and were run differently to what BB systems of today are. I think you might be interested in what i'll post tonight on the subject. It might make you think a little differently. Layton

Hold up. Who's saying they will live on light alone? Layton

Wasp: Nope, conclusions and interpretations I'm looking at. I'll also use Ron's own words to show why some of his conclusions seem strange. Plus some interesting stuff from Eric. I'll try and spend a bit of time putting it all coherently in one post tonight. You never know, it might make sense. Layton