Substrates 101

Discussion in 'Substrates' started by agsansoo, Sep 20, 2007.

  1. agsansooWell Known MemberMember

    Shallow Sand Beds

    A shallow sand bed (1" or so of sand) is a good choice for many beginners. This type of substrate offers little or no filtration, but will support some animals that need a sand bed, like fighting conchs, some snails, and sand-mopping sea cucumbers.

    A shallow sand bed is less expensive to install, leaves more space in the tank for other animals, and, to many people, offers the best look. These sand beds might need replacement if the sand fills with nutrients or solidifies. Stocking some animals that stir the sand bed, such as the fighting conchs and sea cucumbers and nassarius snails, will help keep the sand cleaner in the meantime.


    Many saltwater aquarists prefer not to have a substrate at all. This give the aquarist more control of nutrient levels in the aquarium through use of high flow, strong skimming, and manual and mechanical removal of detritus (uneaten food and poop). With no money spent on sand, or animals for the sand. Startup costs are very low, except for a larger protein skimmer. Systems with no substrate are called "bare-bottom" tanks (BB).

    Bare-Bottom tanks became popular with the Berlin Method, using live rock, better skimmer and water flow technology. The goal is to prevent the breakdown of leftover food and waste by removing such detritus before bacteria can begin to consume it. Which leads to higher levels of nitrates.

    This is a common choice of stony coral tanks, often Acropora-dominated, where the strong focus on nutrient levels is thought to aid growth and color. One of the most obvious advantages to this method, no more worrying about sand storms. You can pump up the water flow to 30-40 times the volume of your tank. This also keeps detritus suspended in the water column longer, so it can be filter out of the display tank.

    Deep Sand Beds

    One approach to tank filtration is the live deep sand bed, often called a "DSB". The goal of such a filter is to use organisms in the substrate to consume and export nutrients via various pathways. Nitrogen, for example, can be exported in gas form after processing by anaerobic microbes. Another good thing is denitrification (removal of nitrates). The only bacteria that will remove the nitrates is the anerobic bacteria, which only colonizes in the no-o2 or low-o2 areas.

    The depth of the sand bed should be between 6" (is usually the deepest that is suggested) and 4" a likely minimum for reasonable effectiveness. The sand must be chosen carefully for particle size. Most or all commercial sand mixes are too coarse, so some careful research is suggested. Oolitic aragonite sand is the prefered sand for a DSB.

    One problem cited with DSBs has been tank "crashes". In cases like this, the sandbed is said to fill with nutrients and then leach them into the water, or become covered with algal or microbial growth. What the precise problem is and the actual causes are debated, but removal of the sandbed might be required.


    This is the ongoing debate among saltwater aquarists, between DSB (deep sand bed) vs. BB (bare bottom). The DSB has been blamed as nutrient sink (or septic tank). Once this septic tank fills up with detritus in about 3 years, your tank will crash. BB tanks are a new & better way of of keeping a saltwater tank. If you are into SPS, with better skimmer technology now of days, one should do away with the DSB & just do BB. Some aquarists just don't like the looks of the BB tanks. Plus all the maintenance from cleaning the bottom every few days, can be a challenge.

    In general, coarser substrates require regular siphon-cleaning because they trap more detritus (leftover food and poop) than fine-grained substrates.

    Good luck on your choice of substrate ! Hope this helps.

    Last edited: Sep 20, 2007
  2. leximommyValued MemberMember

    well this just ruins my day lol
  3. bhcaaronWell Known MemberMember

    Andy, this really help, but, I agree with LexiMommy... ARGH! This ruins my day. And, thus, a tear is shed! lol

    However!!!! If this crashing only occurs, on average I'm assuming, every three years, then it can be avoided if it is replaced every two, right? (Doing partial removal over a period of time to avoid a mini-cycle).

    However #2!! If I decide on an actual functioning substrate (4-6 inches) woudl I not be able to do a reef? Also, I was hoping to do a sand pool (having a large area of sand bed but also having coarser substrate to have a ocean/beach type look), would this prevent me from having a reef tank? (gulp)
  4. leximommyValued MemberMember

    hey i was thinking about that mixed substrate thingy! lol let me know if it works since youll have yours up before i will probley....
  5. bhcaaronWell Known MemberMember

    Oh, i'm not so sure. I too have other things comming up. I need a second job... :'(
  6. leximommyValued MemberMember

    lol whys that?
  7. bhcaaronWell Known MemberMember

    I owe, I owe, so of to work I go! lol

    Besides, this pretty lil new hobby I found will cost me. I need it though.
  8. leximommyValued MemberMember

    lol ok i know the feeling
  9. agsansooWell Known MemberMember

    Crashes don't have to occur, they will if the sand bed is not maintained. Also 3 years is an average. The larger your system, the longer the time it takes to fill up.

    However #2 ... Yes you can have a reef with a 4"-6" sand bed. Just you water flow will be lower to avoid sand storms. Not sure why you want to mix course and fine substrates ?
    Finer particles always sink to the bottom, over time.
  10. leximommyValued MemberMember

    what if you did like this


    -being smaller substrate
    and " being larger substrate....

    like not layer them, but put them side by side in the tank
  11. agsansooWell Known MemberMember

    Why ? If you don't mind me asking. What's the advantage ?

    I did something like this in my tank ... To get rid of some of the crushed coral. I had course crushed coral under my live rock, than added fine oolitic sand around the edges of the glass.
    It looked great for a few weeks, until my snails, starfish and female clown mixed it all up.
  12. bhcaaronWell Known MemberMember

    Actually that was my intention. Like an ocean/beach remember? so the sand would look like the beach and the corser look like the ocean. But, I think I found a solution. Drs. Foster and Smith's new catalog, which I just received over the mail, woo hoo, has a Fluidized Bed Filter by Pentair Aquatics on page 19. Basically it keeps the sand in a canister where water flows through it. I would imagine since the flow of the water is from bottom up, and the flow can be up to 200gph there should be no danger of accumulating gasses. Also, the water is filtered before it enters the canister, so no build up of anything harmful in the sand.

    There is one you can fill with 9lbs of sand, this would be awesome. This adds to the filtration of the entire system, you'll have the added benefit of live sand and you'll never have to mess with it. If anything goes wrong, cut circulation, dump the sand, cycle new sand and start over, no messy clean ups.

    The Major DOWN side is... no stars and limited clean up crew, plus I want sand :'(

    Needless to say, I'm not yet sure. I want sand and what's best for the entire tank. This would mean the Fluidized Bed Filter would be the answer, but, I like the sand look =(

    Oh, what to do? What do-do? Oops, I mean, to do?
  13. giordanopgValued MemberMember

    What about having a BB or a shallow sand bed, and having a DSB in a sump below the tank?
    Would this work? Where would the DSB have to be placed. I'm guessing after the skimmer and before a power filter.
  14. bhcaaronWell Known MemberMember

    Actually, I haven't gotten to that part. But, IF I remember correctly, it required no holes, so I imagin one separate tube off the back of the tank, but, you can probably connect it any way you want. And you don't need a sump to put it in since it is a self contained cannister. You can purchase it separately or as a part of a multy canister, mullti step filtration system.

    As for going BB (BOY! I'm so not used to this term!), that's what I don't want and having difficulty making a decision. But, luckily I still have time. It'll be a few months before I can get anything started.
  15. leximommyValued MemberMember

    that would be a good idea....but.... hers what im thinking, i like the invertabrates, but without sand i cant have them, but i dont like the idea of a sandstorm. but i also do like the idea of having to vac a BB tank every few days....
  16. bhcaaronWell Known MemberMember

    Now you're sounding like me lol

    Now back to you're original post on the mater...

    Substrate or no substrate? (oh, wait, that was sump on your threat, but, same applies)

  17. agsansooWell Known MemberMember

    Fluidized Bed Filters have fallen out of favor. They become nitrate factories. Has to do with aerobic bacteria vs. anerobic bacteria.
  18. agsansooWell Known MemberMember

    Substrate of choice for DSB is CaribSea Aragamax Oolitic Select Reef Sand or CaribSea Aragamax Sugar-Sized Reef Sand. I also thought about black sand, like some of the beaches on Maui (CaribSea Tropic Isle Tahitian Moon Sand).
  19. bhcaaronWell Known MemberMember

    Just when I was starting to get excited about those FBF! Has anyone found a way to fix this? Perhaps by adding something or taking somehting away? (I'm talking plants or animal life, I would like to do as much of this with out chemicals as possible.)

    I had not thought about different color sand. Perhaps instead of coarse and fine sand decoration I will be able to achieve the same result with white and black sand. I also was reading that I can mix Dartfish, Dragonets, Gobies and Jawfish with horsies (I know that I'd have to be careful with the mix and keep an eye out for my horsies). However, I will need sand for this mix so.... SAND IS IN! YAYY!
  20. michaelb323Valued MemberMember

    After reading this I went and bought 10lbs of fine live sand for my 55gallon tank. My thinking is that I wand some filtration, but be able to dig to the bottom to clear all the waste.