Design of a semi-open or open system reef tank

[ritchie1]

Anybody have any ideas in designing a semi-open or open system reef tank? I live about 50 meters from the shoreline and plan of pumping water from the ocean to a plastic water tank in an airconditioned room where the aquarium is, to equalize the temperature. Once the temps are equal, pump it into the aquarium (overflow). The shoreline is sandy and frequently contains a lot of debris like dead leaves, branches, etc. The clearer water is usually (depending on weather and season) about 200 to 300 meters from the shoreline.

Alternative:
Leave the aquarium outside and pump the water directly into the aquarium. This saves electricity with respect to cooling. But the problem is the debris near the shoreline and high sea surface temps. Currently sea surface temps are near 31 C. How deep would I have to go to get lower sea temperatures of around 27 C?

Is it as simple as running PVC pipes connected to the pump inside the house? Can i just put a plastic screen in the pump intake to prevent sucking debris? Will the pump get damaged when it sucks water that contains some sand?

Anyone know of an industrial pump or commercial pump not normally used in aquariums that can be used? I found a brass one here normally used to pump water out of fishing boats, but that will probably not work as brass contains copper....Finding aquarium pumps (not to mention supplies) is very difficult here.

 

[Oscer]

I like the water tank Idea, but how clean is the sea water in you area (as in sewage and soluble contaminants). I would in corporate some kind of pre-filter containing carbon and something to stop debris, before the water reaches the tank.

Is it as simple as running PVC pipes connected to the pump inside the house? Can I just put a plastic screen in the pump intake to prevent sucking debris? Will the pump get damaged when it sucks water that contains some sand?

Well firstly I think you should find out what the costal regulations are and what permits you will need to acquirer, unless you wish to run this system illegally.

I'd skip the screen (or get one with large holes) as this will have to be cleaned/inspected regularly in case of blockage. An option would be to drill holes or cut slots of appropriate size for the fist meter of the pipe at the intake end, and cap the actual end of the pipe. The pump should have some type of screen (often called a leaf catcher) to block large debris.

Over the long term the sand may cause the pump to fail, so it is advice to place the pump intake well of the sea bottom. This should also ensure less debris. Over time some fine particles my collect in the water tank.

PVC or even concrete type pipes should work. The pipe should be of large bore to minimize blockage. 250-350 meters is quite a lot of pipe.

I'm guessing about 15-20 meters should bring the temp down, but I'm not sure.

So far this is a semi-open system in my mined which is best for smaller tanks (under 1500L or so)
How big is your tank? And what turnover do you plan? Will you still have filtration for the display tank?

 

[ritchie1]

Thanks for the reply.

The seawater tested nearly 0 for phosphates and nitrates...I would think the water is rather clean as it's is away from the city. I've attached a picture of the area. Most of the people here make their living either by fishing or farming. There are no factories. There might be some coliforms from the nearby houses... will try to get a water analysis of the seawater. The natural seawater here has been used in a closed system reef tank for about a month and everything looks ok so far...

Good idea on the prefilter and putting holes on first meter of the the pipe intake. Will use the white filter floss for prefilter. Will try to look for the leafcatcher, perhaps from swimming pool product suppliers.

I was initially thinking of using 1/2 inch pipes but now that you mention clogging, thinking of getting bigger ones. I remember reading in a web page of i think it was monterey bay aquarium that once a week they shut off their pumps w/ pipes going to/from the sea to their aquarium in order to remove the clogging from the animals that attach to the pipes. What minimum bore size do you recommend? Can probably get up to 2 in pipes but this will be very expensive for 300 meters of pipe. Perhaps thicker pipes would also be better to minimize maintainance on broken/cracked pipes.

OPEN SYSTEM
My main aquarium is 250 gallons. If I do run the pipes out to 300 or more meters and cooler waters, thinking of running an open system to save on electricity cooling and lighting the tank, among others. Will leave the aquarium outside and use natural sunlight. This aquarium outside will be connected to another one inside so I can control the temperature in case the pump/pipes going to the sea will have to be shut down for maintenance or the sea is murky. Thinking of about 2000 liters per hour turnover with the ocean if i do run an open system. Protein skimming will still be used in the aquarium as its main filtration, but this may not be necessary for a 2000 liters/hour turn over.

SEMI-OPEN SYSTEM
If the intake of the pipes are only placed several meters from the shoreline, then it has to be a semi-open system (using the water tank to equalize temps first) with turn over of about 150 gallons per day(or every other day). In this semi-open system protein skimming will be used and perhaps also additions of kalkwasser.

I'd like to run an open system as much as possible with only accasional shut-offs for maintenance, but is an open system is economically feasible to run over time? I can spend a lot on building the system, but not if it is very expensive to run maintenance-wise...

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[ritchie1]

Here's a picture of the area

 

[Oscer]

Your sea water doesn’t look bad at all. But it's best to get a proper analysis.

Yes, often a pool pump has a built in leaf-catcher, and it can handle salt water so it is a viable option.

I remember reading in a web page of i think it was monterey bay aquarium that once a week they shut off their pumps w/ pipes going to/from the sea to their aquarium in order to remove the clogging from the animals that attach to the pipes. What minimum bore size do you recommend?

I also have stumbled across this web page. The main reason for them do this (to my knowledge) is because they use pipes of large bore that are not necessarily screened very well thus animals can enter and feed of the strong flow. But cleaning at that degree I think will not be required in your setup. The minimum bore is probably dependent on your pump intake bore, but I recommend at least 35mm (+-1 1/2 in). 2 in would be great.

I would recommend you fined out the depth at which you will have to place the pipes to attain the water temp you desire. Extra thick pipes should not be needed, rather get ones with a bigger bore. I mean small cracks in the pipe will not happen for no reason and if they d o occur, it should pose no problem as long as the cracks are submerged.

In the open system, the need for a skimmer is not critical as long as debris can be kept in motion by extra water flow. Your idea seems quite plausible. The problem will come in at the time of maintenance, as you will have to inspect the pipe line at least once a year or so and when a blockage occurs. But is 300 meters realy required?

In the semi-open system the additions of kalkwasser will not be necessary, unless the sea is lacking.

Well compared to what it would cost you filtration wise, to run the tank in the same way as you can run it in the open system. It is extremely economical.

For example: If you add 100 clown fish to your tank, which require an amount of filtration at X price. You pay the X price to install the open system and now you can house 400 clown fish and still stock corals, or as much as your tank can take (physically). So an open system is a dream in other words.

Running Cost
Well, yes running a large pump and the extra water motion (Not necessarily more than a good reef tank should have, but a fare amount) my seem heavy, but if you do put the tank out side and no lighting is required then it is probably more economical, only concerning money for running. Even if you put it inside and add the best lighting, you still don’t need a skimmer, reactors, additives and salt mixes, only a bit of carbon and filter floss.

 

[ritchie1]

Thanks again, Oscer!

Will be doing further tests on the water and i'll inspect the area to determine the proper distance from shore and the depth to cooler waters.

I'll post here as the system is built within the next few months.

 

[ritchie1]

Someone suggested to me building a seawater well like the one used in the waikiki aquarium instead of the open ocean intake. Will the water be normally suitable for a reef tank if i go deep enough...the groundwater we use contains very high levels of nitrate and phosphate? Anybody know details on the waikiki aquarium seawater well system?

 

[ritchie1]

Looks like i'll be postponing this project for a while until i can save some money. Estimated costs are significant...

Ritchie