Help With A VERY Non-Standard System

Hello everyone. You could say I'm new to this hobby and also not really. I've never owned a salt water tank. The largest freshwater tank I've ever had is a 2.5 gallon beta tank.

That said, I am currently in charge of designing and building a 72, 10-gallon aquarium system. This is an academic research system used for biogeochemistry experiments. As such, my requirements and limitations are a bit different than most. We control for water chemistry and atmospheric chemistry within the tanks as much as possible.

The point I'm hung up on at the moment is designing our filtration system. The current plan is to have sets of 3 tanks (30 gallons total) draining via overflow into a sump located behind them. All tanks will be drilled so I don't think there is a need for an overflow box, if I am understanding everything correctly. We will have skimmers in each sump and return pumps pushing water through chillers and back to the aquaria.

Limitations:
No bioreactors. These experiments rely heavily on water chemistry, so we can't have random biology (aside from the organisms in question) effecting the water. No sand. No live rock. Bare bottom tanks and sump. One thing we can use is activated carbon.

Space is our other limitation. Obviously, 72 aquaria, 24 sumps, and possbily 24 chillers will take up significant space, so I am doing a lot of squeezing and trying to limit equipment needs.

Advantages:
Doesn't need to be pretty, just organized.

90% of the water will be changed weekly. I am implementing a semi-automatic draining and filling system for the tanks and our water chemistry requires this. We essentially have unlimited water (located at the coast with an installed seawater system) that will be prefiltered through 150-5 um filters and a carbon filter.

No fish. The organisms we study are benthic invertebrates (i.e. corals, clams, red algae, conchs, urchins, etc.)

Ok. After that overly long explanation, here is what I need help with. I've discovered that a canister filter is ill-advised for a saltwater system, and frankly, I'm thrilled about this fact. The real question is, will I need a mechanical filtration system or will the sump/skimmer combination be enough? I'm thinking the sumps will have to be limited to around 20-25 gallons due to space limitations. We have HOBs that we used with a previous system that didn't use sumps that could be used for mechanical/carbon filtration, but my colleague would like to avoid them. We are attempting to limit air exchange with the surrounding atmosphere and these introduce air. The air intake on the skimmers will be using our controlled gas, so that is not an issue there.

I appreciate any advice you all can provide. I've run these systems pre-sumps, so I somewhat know what I'm doing. This is really the last sticking point. Thanks again. (and sorry for the long post)

 

Depending how long the organism in question will be housed and what its byproducts will be will determine what type of filtration you will need. If the organism creates ammonia then the nitrogen cycle will need to be taken care of for example. If you are not filtering biologically then yes a mechanical filter will be needed. A skimmer will remove proteins but will not remove ammonia. Using chemicals to keep the water clean will be tedious and may have a bad effect on the animals long term. I'm sure others will be able to give better advise on setting up and keeping research lab running. BTW if the skimmer has a sponge on it the sponge will populate with nitrifying bacteria making it a biological filter. I'm not sure how steril your wanting to get here but you may be able to use sponges to take care of some of the filtering needs.

 

There are loads of successful tanks out there that run on a skimmer and no other significant filtration equipment.

I think the concern lots of folks here will express however is the lack of rock. Glass and plastic are going to allow only a few types and limited quantities of bacteria to grow. That means ammonia will build up, nitrate will build up, and nitrate will build up.

Given the huge water changes you're describing, the last won't be a problem, but I don't think any of us think you're gonna have much luck with corals if you can't stabilize the first two. Perhaps the lack of fish means a lack of significant nutrients - and therefore no issues.

The other problem you're going to have is this system sounds like its inclined to be inherently unstable. That in itself could be a problem for your livestock.

Let me ask this. What do you mean exactly by random biology? Are you actively taking steps to exclude all bacteria? If not, why not just include some live rock that starts out sterile. If you're really building a sterile environment however, why bother skimming at all. Just change enough water to keep it all happy.

 

Addition of anything to the system that could possible alter the carbonate chemistry (i.e. carbonate material that could buffer the system or respiration unrelated to the organisms in question) of the water is the concern with these systems. We make very precise measurements of alkalinity and DIC, along with the usual T, pH, and salinity. This is why sand and live rock cannot be included. Any system buffering by something other than the organisms themselves is unacceptable.

We have successfully run many experiments this way, except we used HOB filters with mechanical filtration and activated carbon in individual tanks instead of a sump/skimmer system. So, that is essentially all that is changing for us. The main concern for us is breakdown of food in the system (dried green algae and frozen brine shrimp normally).

 

Questions:

- Is there a reason you're not running the entire system off a single, large filtration system?

- You say "no bioreactors" - does that mean no biological filtration at all (e.g. something like bioballs)?

- You mention changing 90% of the water weekly. Is that a single change or multiple smaller changes?

 

We can't do a single filtration system because we run multiple water conditions at the same time (i.e. different temperatures, different water chemsitry, etc.) So, mixing the waters between treatments doesn't work.

We can't do any biological filtration of ANY sort. Any respiration by organisms that aren't being studied will affect the water chemistry. There will always be some natural growth of algae and such, but we do our best to minimize this as much as possible.

The 90% water changes are all at once. Once a week the water is drained from the tank and then refilled. The water that is added back in is preconditioned to have as close to the same conditions as possible.

Like I said, this is VERY different from what everyone else here is used to and probably goes against most of the standard procedures for a salt water aquarium. We are going out of our way to stress the organisms, because that is what we are studying, but we need to control what the overriding stress is.

I think we are going to go with a simple mechanical and activated carbon filtration box inside the sump that the overflow water will go through before it dumps into the sump/skimmer and then return to the tanks.

Thanks for your help.

 

Have you considered how much ammonia will build up in a week's time? Without knowing your expected bioload and nutrient additions it's tough to say if it will become an issue. Under most normal aquarium situations you'd start to get noticeable amounts by then.

Not sure if the ammonia spikes would impact your experiment. If so, you could consider doing smaller, more frequent water changes.