Substrate Review – Sand Beds and Bare-Bottom Tanks
By: Scott Zachow
Substrate Review – Sand Beds and Bare-Bottom Tanks
This month, I wanted to do a different type of review than what we are used to, something different for the New Year I suppose. With all of the discussions over the past several years about substrate, I wanted to share my review on sand beds and bare-bottom tanks.
For the past 8 months, I have been personally running a bare-bottom reef tank, which is a tank that has no substrate, what so ever. Over the course of the years that I have been a hobbyist, I have run with many different types of substrate including crushed coral, fine particle sand and now the lack of any substrate; each of these having their own advantages and disadvantages which I hope to outline for you as a hobbyist. I am not suggesting or advocating the use of a bare-bottom reef tank over one of the other many methods, simply hoping to describe my experiences.
A picture of the authors M. capricornas showing the coralline algae covered bare-bottom.
Bare-Bottom tanks became popular with the Berlin Method; a methodology that relied solely on the use of liverock for biological filtration and heavy protein skimming. The thought behind eliminating substrate with this method was that the aquarist could easily siphon the detritus that inevitably builds up at the bottom of the reef before it was broken down and led to nitrates; obviously a challenge for all aquarist.
Live Deep Sand Bed
I enjoyed and had great success with the use of deep, fine particle sand beds that over time became populated with lots of nitrifying bacteria as well as various detritivores that helped stir the sand and process uneaten foods. I seeded my dry sand with live sand from many different sources; fellow hobbyist are usually willing to share a cup of sand, suppliers that sell live sand (collected, not the bagged stuff sold as live sand) and also bought kits from online stores that sell bristle worms and other sifters for a sand bed. The diversity was great and I enjoyed not only the benefits of having the additional biological filtration and nitrate reducing capacity that a live sand bed offers, but the excitement of gazing at the different life which thrives in this type of environment. Having a sand bed was a great experience however there was one large set back, the inability to really add a lot of water flow to our reef. We keep a Small Polyped Stony (SPS) and Clam dominated reef, which need to have a high level of total water flow. I like to think that turning over the total water volume of a system 30 times is minimal water flow for this type of reef. We were turning over only the total water volume in our 75 gallon reef about 20 times utilizing Maxi Jet powerheads and our sump return pump. This was about the maximum we could get without causing a large sand storm, which was a constant mess. An additional problem that anyone can relate to is the suction cups on powerheads all too frequently fail, causing a much larger sand storm and displacing large portions of the sand. Not only was the cloud disturbing, but the rapid change in redox and the waste suddenly being disturb has caused RTN on some SPS and some people have even reported loosing the majority of their tank.
This is typically how a new tank will look for several days after using a deep fine particle grade sand. Some of the cloudiness can be mitigated by rinsing however the various grain size, including the “powder” that causes the storm, is what you want so rinsing is not recommended. Picture courtesy of George Davis.
The cost and availability of the correct sand is also limiting at times. Obviously over the years there has been a big push for Southdown Sand and Yardright sand due to it’s cost. At $3.50 per 40-50lb bag, this is the most economical choice but its availability is limited to the hardware stores in Ohio, Pennsylvania and most commonly New England. At times, even a long time ago we at Reefland, people will luck into a large quantity of this sand and have it shipped to them. To help offset the cost, they would sell it at cost or for a slight markup to folks that didn’t have it available to them. Lucking into this is not very common unfortunately. This leaves people going for other, much more expensive alternatives such as Carib Sea, ESV Oolitic sand or others. At rates of better than $30.00 for 30lb bags, this can be very cost prohibitive but at least it’s readily available. There is an added cost to setting up live sand beds and that is to make them live. Remember, diversity is the key to a thriving sand bed therefore its important to pick up seeding kits that are sold at various online retailers in addition to collected live sand. As mentioned above some of this cost can be mitigated if you are fortunate to have some fellow reefkeepers near that are willing to supply you with a cup of their live sand bed to help kick start things.
A developing sand bed displaying lots of color from Cyanobacteria. The bubbles rising up through the bed are nitrogen gas; showing that the biological filter desired is performing. Picture courtesy of George Davis.
When looking for sand for your aquarium, you should look for aragonite sand (Calcium Carbonate). People have used and reported success with silica sand however for the ease of mind, aragonite is my recommendation. Besides knowing 100% that it is safe, the aragonite provides some additional buffering capabilities and the sand does dissolve which, albeit little does help the calcium level in your reef.
My decision to go bare-bottom with our current reef was simply because I could not add as much water flow as I wanted. Our 75-gallon reef is not drilled for a closed loop and my attempts at building one were miserable so we could only use internal water flow options. The Tunze Stream pumps seemed like a perfect choice however reports online from people with much large aquariums than ours, who also used sand beds were that the pumps were much too strong and caused sand storms and displaced large portions of their sand bed. Wanting to go with at least 50x turn over, I had to make the trade-off.
After running a bare-bottom tank for nearly 8 months, I can tell you that there is the same number of advantages and disadvantages as running a deep live sand bed; one of the most obvious advantages to this method, no more worrying about sand storms. We have placed 2 Tunze Stream 6060’s, 4 Maxi Jet 1200’s and our return pump in a 75-gallon reef with excellent results, turning over the total water volume over 70 times per hour! This may sound like a lot but I think we could even use more. I have no worries about the Maxi Jet’s suction cups failing, and no worries about a large displacement of sand causing problems with our coral.
Having this high level of flow has also helped with the detritus in the tank, although there are still a few spots that it accumulates. Since we have some spots that do accumulate detritus, it is necessary to siphon the bottom of the tank at least bi-weekly. It is even more difficult to siphon the bottom of the tank under the reef structure. I thought that with the high level of flow this would not be a problem however it still accumulates. This task is a disadvantage of the bare-bottom reef but required to keep nutrients low.
Another down fall to the bare-bottom approach, it isn’t as aesthetically pleasing, especially in the beginning. Over time, our tanks bottom has become covered with bright purple coralline algae to which corals can easily be attached to, however it is not as nice as a bright white sand, and has no where near the light reflectivity. To offset this, people have begun using white cutting boards and other material, and it also helps to protect the glass bottom from a falling rock if your reef structure is not secure. I personally opted to take several hours placing the liverock in our tank to ensure it was stable and to not have that concern. There is also a definite reduction in the small detritivores on the bare-bottom aquarium, which is something that I miss personally. The worms, mini-stars, Nassarius sp. snails are all little invertebrates that are missed from our marine aquarium.
he authors 75 gallon reef only 2 weeks after it was transferred. The new look of a bare-bottom tank takes some getting used to, especially when you see nothing but glass at the bottom. This is quickly covered with coralline algae which softens the appearance.
Running a small 75 gallon aquarium, the bare-bottom approach was a feasible option for me. I would choose to run a bare-bottom method in any aquarium that I set-up that is smaller than 120 gallons. If I ever set-up a larger aquarium, larger than a 120 gallon, I would most likely move back to a deep sand bed to mitigate the maintenance that is required without one.
As with any other decision in this hobby, each methodology and option should be considered before taking any first steps. Different methods will require different equipment, maintenance routines and dollars to do. Whether choosing between different lighting options or different substrate choices, make sure to research the pro’s and con’s of each before it’s too late.
Regards,
Scott Zachow