Question 1
Dear Albert,
I am thinking about converting my 100 gallon reef tank to the Berlin method of filtration. Currently I have about 150 lbs. of live rock which is held off the bottom of the tank about 1 1/2" by egg crate. There is no substrate in the bottom of the tank. The tank houses over 20 specimens of hard corals, soft corals, polyps, photosynthetic gorgonias and tridacna clams. I also have a marroon clown and a six-lined wrasse to control nasty pests. I have already begun to pull the media out of the wet/dry portion of the filter. Additional filtration is provided by a good protein skimmer. I have read a number of articles about the Berlin method, including the ones in your library. However, I am still not quite sure of the best approach for my tank. Unfortunately the tank is fairly narrow and there's not a lot of room between the front of the tank and the begining of the live rock (about 2"). Your article mentions construction of a dam using a thin sheet of acrylic. I was wondering why you suggest this method as oppossed to placing live sand throughout the bottom of the tank. This is what I was thinking of doing. My only reservations would be that sand, which is placed underneath the egg crate, would act as a nutrient sink and the benthos would have a difficult time accessing this area. Any ideas, suggestions or opinions would be greatly appreciated. Thanks
Answer:
What you are doing is fine. Removing the biomedia slowly is the right manner in which to convert from a trickle filter type system to a Berlin one. You can find out whether you are removing material too rapidly by checking for the presence of ammonia and/or nitrite. If none is present you are not going too fast and the biofiltration that was occuring on the media is transfering itself to the rock's insides. Mind you even with the biomedia some of the rock is already performing that function anyway. Bacteria settle anywhere convenient and will populate the inside of the rock even when other filtration media are present.
Good skimming is necessary to ensure that organics do not build up and that your DO stays at high levels.
Removing the media eliminates areas where decompostion can take place and where anaerobic activity may start (I say may as it does not necessarily do so).
Since you state that you have plenty of rock the filtration you will end up will be just fine and able to handle quite a large load. Again testing will tell you when to add animals and when not. Should ammonia and/or nitrite appear you need to evaluate why. Is the tank overloaded or have you added too many animals too fast. This is easy to solve as you can always back off for a while until the water is ok again.
Adding sand in a tank such as yours is a little more difficult because you do not have a bar bottom tank. There are grids and the sand will fall through unless you cover it with a fine mesh screen. This is do-able but a lot of work. Consider running the sand in your sump as opposed to in the tank. Since you have the sump and need for the skimmer anyway, you can add a nice layer of live sand there, without running into the possible problems that may develop if you were to add it to the tank. This seems the best way to go in my honest opinion and convert to a LS and LR system.
Question 2
The egg crate is not sitting directly on the bottom of the tank. It is supported by short PVC legs about an inch off the bottom. Live sand could be placed underneath the egg crating without much of a problem. I would like to put sand in not only filtration, but also for aesthetic purposes. I have heard that putting sand directly on the bottom can lead to hydrogen sulfide problems. It is also my understanding that if you have enough detritivores which continually turn over the sand, that this problem can be eliminated. Would this be a problem with live sand placed underneath the egg crate? In essence what I would be doing is placing a layer of live sand (approximately 1 1/2") on the bottom of the tank and then placing live rock directly on top of this. Are there any concerns I should be aware of in using this technique? Thanks
Answer
I understand the set up you describe and figured from your previous message that you had in fact done it that way to allow for space underneath where detritus can accumulate and then be easily removed.
If the sand is not too fine, as explained in article I wrote about live sand which is in the DL for a small fee section of our web page, then packing of the sand will not be a problem and you will not risk the formation of anaerobic areas. Of course, adding the stirrers and sifters is an excellent idea but if they cannot get through the eggcrate then they cannot do very much for you. Perhaps something to consider is to remove the eggcrate altogether and set the rock on the sand.
If you leave the eggcrate and use small sand dwellers (e.g. from one of the mail order places) you will get enough movement in there to prevent anaerobes.
As long as the sand is not too fine and does not pack and you have sand dwellers you will have a fully functional and safe live sand live rock system as the end result.
So you now have two alternatives: the one where you place the sand in the sump and the one described here. Of course, even if you place sand in the tank you can still add some more in the sump. There is no contra-indication. You could even make a refugium out of the one in the sump.
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