FOWLR and Filtration

[Saclem]

I have a 75 gallon FOWLR Aquarium that has been set up for about 8 weeks. All my levels look good. I have a very slight level of nitrate and assume as long as you have some fish you're going to have some nitrates. I have 21 pounds of live rock, which is all I want to have. I also have some other rock that I don't know its proper name, but for purposes of this message we will call it base rock which currently has no live growth on it. I have a pretty good understanding of the hazards of overstocking and overfeeding and the effects that it can have on a tank. I had a salt water aquarium with some success about 14 years ago and have had small fresh water aquariums all my life. My setup, including the 21 pounds of live rock is live sand substrate, 4 power heads, a 20 gallon sump with a trickle filter/ bio balls, as well as a skimmer. My question is -- Between the 21 pounds of live rock, trickle filter and skimmer, is this a recipe for disaster with ammonia and nitrates? If I commit to doing 10% water changes about every 2 weeks will the setup I described have success? Success being measured by the fact that the fish live and the tank is not overrun with algae. I realize that adding more live rock and just running a skimmer is the recommended way to manage a tank. However, for the basis of my question I would like to know the plus and minuses of what I have described.

Thanks for your advice.

[Ninong]

Hi Saclem,




We have a separate forum for FOWLR questions, so I will move your thread to that forum.

[leebca]

You pose a good question. A hobbyist doesn't have to have the 'proper' amount of live rock for a FOWLR system (usually about 2X the gallonage in pounds) to operate properly. Just as long as there is sufficient biological filtration. However, more info is needed to answer your questions accurately.

What isn't clear is the total circulation within the aquarium. I am not familiar with the flow rates of the equipment listed, so you need to give me a total flow rate.

Total flow rate is determined by adding up all the flow from each pump (internal and external) that moves water into and around the display tank.

The unit of measurement is gallons/hour or the number of times your total volume of the system is turned over, each hour.

Also, I will need to know the total volume of water in the system.

I want to know what substrate you're using, the depth, the particles size range. You wrote 'live sand' but that isn't clear -- is it really sand (like on an average beach) or different sized particles? The depth of this is important. Also, need to know how much 'dead rock' is in the aquarium.

The trickle filter doesn't tell me its size or content. More info on this is needed to answer your questions accurately. A photo would be helpful in addition to the above info.

You don't need live rock at all, to run a successful FO system, and as noted above, less than the recommended quantity for a FOWLR system is possible. It just requires you have enough biological filtration which is tied to the following:
flow rate
surface area
sizing of biological filter
and other system features.

[Saclem]

Hi Lee,

Thank you for the reply to my question. I will get the totals listed shortly.

[Saclem]

Hi Lee

Here are the answers to your questions:
>
> For calculating my total water flow I am basing it off the following:
>
> For PowerHeads I have two Aquaclear 70's and a Aquaclear 50. The 50
> has a FLO rotating deflector attached (which appears to reduce the
> flow rate.) All three of these Powerheads are being run through a
> Tsunami Wavemaker. I also have one Hydor Koralia pump 2 which is
> constantly running. For calculation purposes the Aquaclear 70 appears
> to be rated at 400 GPH flow rate and the 50 is 270 GPH flow rate.
> Since they are on a Wavemaker and alternating on/off I am allowing
> for 400 GPH for the 70's and 135 GPH for the 50. I am leaving the
> Koralia at the 600 rate, which does not appear accurate
> based on viewing the water movement. For the sump I believe I have
> a Quite One 3000. This was given to me with the aquarium, so I'm not
> positive on the brand and there are no markings on the pump. A 3,000 is rated at 780 GPH,
> I am allowing 300 GPH for my calculation.
>
> Based on the totals above I get a total flow rate of 1,435 GPH. My
> tank does not look like it is moving that much water.
>
> The total amount of water in my tank is 68 gallons between the
> aquarium, overflow box and the sump.
>
> I have 120 pounds of Natures Ocean Reef Sand. Which is about 2-3" of
> substrate.
>
> I have one 42 pound dead rock, that looks like a half cave. The rest
> is my 21 lbs of live rock.
>
> As for a trickle filter, it is very basic, probably 10 - 15 years old.
> It sits on top of a regular 20 gallon high aquarium that is
> functioning as the sump. The trickle filters measurements are 11"
> wide X 9" long X 15" tall. It has one drawer that is about 2 1/2"
> thick. I currently have a blue bonded filter pad and a more course
> ridged pad in the drawer. The trickle filter contains basic bio-balls.
>
> I did not want to go with only a FO system because I like some of the
> fish and invertebrates that do best with live rock.
>
> Thanks for any insight you can provide.

[leebca]

The flow rate is a bit tricky. I like it that you were conservatively estimating the flow. There are many things which detract from manufacturer's ratings. Every elbow adds about one foot of back pressure. Every foot rise is another foot back pressure. Every 10 feet of piping adds about one foot of back pressure. Powerful pumps can be reduced to a trickle when plumbed into certain configurations.

The thing I don't care much for is the wave maker. The fish don't need this, and at the same time, this is not particularly optimal for biological and mechanical filtration. If you can imagine, the water moves back and forth rather than through and past the structures and substrate. I would take out the wave maker and angle the internal power heads towards 'dead areas' of the tank. Leave no place without water movement of some sort. I could then buy into your setup as having enough water movement and flow. You want water to flow around and through everywhere and then to carry bits and particulates to the mechanical filter.

The other information regarding the trickle filter is good. I would say the compensation of that filter makes up for the live rock shortage. That is to say, I believe you have enough biological filtration to handle a FOWLR system with normal stocking.

The substrate depth is in a 'no-man's land' area. Too thick for a normal substrate, yet not thick enough for a deep sand bed. This may cause problems down the road. My preference would be to cut the substrate depth in half. If you really want sand borrowing fishes, however, keep a part of it at about that depth and introduce a lot of sand-moving/sand-sifting benthic creatures.

Other than the above, it seems to me the system would provide a good environment for marine fishes.