sand vs crushed coral vs mix of the two

[keeplearning]

I currently have a crushed coral substrate. I have read and heard many good things about using sand in general, especially deep sand bed, so I have been considering my options. Would like to know what you guys think the pros and cons are. Thanks.

[Chris]

Deep sand beds are pretty old school. I would go with just sand or mostly sand and a little crushed coral or larger grain sand mix especially if your going to have certain gobies/jawfish that burrow in the sand so they can construct their sand cave

[keeplearning]

I dont plann on keeping a jawfish although I do love them. I am more concerned about it trapping detritus and the ensuing nitrates.

[CalmSeasQuest]

I think your concerns about the potential for trapped detritus causing increased Nitrates are valid. I use arrogonite, formerly Caribsea Special Grade Reef but for the last two builds I've used Tropic Eden which I now prefer as to my eye, it's brighter and is much cleaner.

With the exception of very shallow tanks, I have always used a DSB and have never had any issues with Nitrates. In addition to water changes, there are now alternative ways to lowers Nitrates (bio pellets, denitrators....) but being "old school" I tend to stay with what I know, and what has worked for me in the past.

Regardless the depth debate, if it were my tank - I'd ditch the crushed coral.

[keeplearning]

How deep of a sand bed are you using Tom? Do you use it in the display or in the sump/fuge? Any opi.ions on mixing to two? Removal of existing substrate qould be a very labor intesive and time consuming process.

[CalmSeasQuest]

5" in DT. That tank has been up for a little over 3 years - Post cycle, I've never been able to detect any Nitrates.

My knowledge of nitrate removal is limited as I've never had to deal with the issue. If your substrate is the source of your nitrates, I'm not sure how adding sand will help. Over time, the sand will settle to the bottom. Perhaps slowly removing the cc as sand is added?

As for mixing, I wouldn't use any more than a spattering of CC on the surface for burrowers to use to shore up entrances.

[MyNemesis]

The rule of thumb with sand beds is less than one inch or more than three inches. The reason for this is that the anaerobic bacteria inhabit the bottom inch and a half and the aerobic bacteria are contained in the top portion. I have a piece of eggcrate buried at 1 and 1/2 inches suspended on cut PVC pieces to prevent any unintended disruption of the lower layer that can cause some problems. I also did that to prevent rock shifts from the jawfish I had at the time. If you mix the crushed coral and sand, you lose the benefit of the sand bed. Get rid of all your crushed coral that is causing any nitrate problems you have and switch it over. You can do it in a weekend and you will be thrilled with the results!

[jimsflies]

The theory of a deep sand bed is to remove nitrates. It does this by creating anoxic or anaerobic zones where denitrifying bacteria thrive. With that said, I don't care for a dsb in a display tank.

I would personally not consider a crushed coral only substrate due to the potential to trap detritus and increase nutrient levels. (by "Trap" I mean...settle in areas where it can not be consumed by cleanup crew or entrained in the water column to be processed by your mechanical filtration.) I think a deep crushed coral bed would be disasterous.

I like fine sand the best. How fine depends on how much flow you have as finer sand easily gets stired up. Although after a couple weeks it tends to stay put better due to bacteria building up on the sand particles. I use a little crushed coral where I want the pistol shrimp/jawfish ect. to hang out so that they can build a stable home.

[AZDesertRat]

I have a 5-6", 330 lb. Southdown sugar sized DSB in my 100G display that is over 8 years old and never been touched or vacuumed. Nitrates and phosphates are undetectable and it is as whits as the day it was installed.
I have had shallow sand beds, crushed coral and bare bottom over the past 30 years but love my DSB tanks.

If you mix grades of sand or crushed coral and sand the coarse materials will always rise to the top. I don't care for the looks of coarse material nor like the fact it traps detritus myself.

My flow is two Evolutions 1400's on a Reefkeeper Lite switching every 30 seconds and an OceanRunner 3500 return pump via a Oceans Motions Squirt two way switching device and my sugar sized sand stays in place. Once the colonizing bacteria coats the sand it settles like a rock when disturbed so its not really a proble unless you have digging critters.