View Full Version : So Which is it... Let the debate begin

12-07-2002, 05:13 PM
re-reading this post I figure it sounded bad, so here is and intro... I have read to conflicting threads on this forum and would like all of your valuable input.

This thread is in regards to deeper sand substrate provides good biological filtration. http://www.cichlidforums.com/viewtopic.php?t=20


This thread is in regards to shallower sand substrate prevents harmful build up in the sand which can hurt your fish. http://www.cichlidforums.com/viewtopic.php?t=613

So lets get some educated input, references welcome to determine which it is.

I tend toward 4"+ is good, but you have to do propre maintenance.


12-09-2002, 11:09 AM
I think 4"+ would be great if you could cycle your tank water through the sand bed. Then you would have a giant fluidized bed filter. I guess you could accomplish that by using a reverse flow powerhead and allowing the water to bubble up from under the sand bed, but I would think this might cause excessive cloudiness if not done correctly.

Without water flowing through the sand bed, or something aerating the substrate, I would be very concerned about the deep sand bed. I recently put sand in a tank, and not only am I concerned about the sand going septic, but I've got algae growing on the sand surface, I can't really clean in off, and the pleco isn't eating it. It looks like crap.

I hope someone has the correct answer to this question, as I really like the look of sand, but am a bit concerned about using it in the future.

12-09-2002, 02:20 PM
Hey all- Here's where my years of keeping reef tanks will hopefully shed some light on this subject. Deep sand beds are successfully used by reef tank enthusiasts, and a few years back some of them applied the principals to African tanks with not much success. Here are some of the reasons that they work better for reef tanks.

1- Dentrification- Between the salt mixes, trace elements and RO water costs, water changes in the reef tank are expensive. The primary biological benefit to the deep sand bed is anerobic bacteria in the deeper areas will reduce Nitrates, which cuts down on the need for water changes. Keep in mind that you must build a plenum underneath "and" keep the bed relatively undisturbed for this to work. Given how much less expensive fresh, tap water is, this is much more easily accomplished through water changes in a freshwater tank.

2- PH buffering- While this initially seems an attractive benefit, it also doesn't work as well in a freshwater tank. Reef tanks are kept at a PH of right around 8.0, but African tanks should be kept higher. The way it works in a reef tank is that in the deeper areas of the bed, all the biological activity drives the PH down "in the bed only". Your Aragonite/crushed coral will dissolve only "below" PH 8.0, and will buffer the PH. Again this is much more easily accomplished in a fresh water environment through water changes and use of the proper African Salts.

3- Trace Elements- All this Aragonite dissolving in the reef tank frees up building material for the live stony corals. Unless someone is keeping corals in with their africans, this is of no benefit and will not even really happen if the PH is kept higher than 8.0

4- Closed vs. Open Systems- Deep sandbeds are meant to be part of a "closed" system. In other words a system to which almost nothing is added. A typical reef tank with sandbed has almost no fish in it, and only a pinch or two of food a week is added. The fish must mostly feed on the various copepods and other critters that are replicating in the tank. A tankful of frisky cichlids being fed a hearty diet will quickly overwhelm any biological benefit of deep sand and probably clog it up in short order. Combine this with the fact that maintenance will be that much harder, and the the sandbed will take away valuable water gallonage (i.e. living space) from your fish and I'm sure most of you can guess which answer I picked in the survey :wink:

12-09-2002, 07:38 PM
I guess I will hold off on getting more sand....

05-06-2004, 05:59 AM
Thanks Scotty. Good info!

z rock
05-20-2004, 07:36 PM
There can't be biological filtration if there is no oxygen.A deep substrate in a freshwater tank will create methane gas when it gets full of fish waste.Its much easier to clean less substrate.If the substrate is sand.Fish poo can be vacuumed off the top.With gravel it gets mixed in and must be vacuumed frequently.

05-20-2004, 09:13 PM
Originally posted by z rock
There can't be biological filtration if there is no oxygen.

I think you mean there can be no nitrification of wastes in such a scenario (since nitrification requires oxygen). However, the are anaerobic processes that can take place (denitrification is the relevant one) that convert excess nitrate into nitrogen gas, etc. Such processes require an extremely deep sand and undisturbed sand bed though.