Re:90G set up for mandarin,seahorse,coral system etc?

Pete Giwojna

Dear Clintos:

I’m glad you like the picture of the seahorses clustering on the artificial sea rods and gorgonians — it’s always fun to see a group of healthy, multi-colored seahorses hanging out together. The ponies at the photograph are all Mustangs and Sunbursts (Hippocampus erectus) in Dr. Randy Morgan’s new seahorse tank (he is also the photographer). The ponies are perching on the two types of artificial sea rods offered by Living Color. (If you read through the post at the top of this forum titled "Best artificial corals and hitching posts for seahorses," you can see photos of most of the artificial corals and gorgonians I suggested that you consider for your 90-gallon display tank, sir.)

No, as long as you have plenty of suitable hitching posts in your display tank, it isn’t necessary to include macroalgae for the seahorses. Your aquarium system will include algae turf scrubbers so there is really no need for you to add macroalgae in order to help control the nitrates.

For colorful red macroalgae, you may want to consider Botryocladia, which is commonly known as red grapes or red grape Caulerpa (although it is not a species of Caulerpa). It’s very attractive, grows reasonably tall, and won’t take over your aquarium.

Halymenia or dragon’s tongue is another attractive red algae species that is worth your consideration. Red Dictyota is yet another reddish macroalgae that grows tall rather than bushy, which you may want to try. There are a number of good sources where you can obtain colorful macroalgae for the aquarium, Clintos.

For example, Inland Aquatics has perhaps the best selection and variety of macroalgae available, including a number of red types:

Aquacon is another good source for cultured macroalgae:

Click here: Marine Plants for Saltwater aquariums

Be sure to check out as well — they offer a Red Macroalgae Sampler that includes a few different red species, and they also offer Botryocladia and Halymenia on occasion:

In short, Clintos, you need not have any macroalgae in your display tank, but there are a number of attractive species to choose from if you want to go that route. Otherwise, you can get all the benefits the macroalgae provides in terms of nutrient export, nitrate control, and outcompeting nuisance algae by maintaining a lush bed of macroalgae in your 25-gallon sump, rather than in the display tank.

In addition to providing nutrient export and the other advantages mentioned above, the macroalgae in your biological refugium/sump can be maintained on an opposite light cycle to the main tank to offset the daily fluctuations in pH, photosynthesis, dissolved oxygen/carbon dioxide, and redox levels that otherwise occur in the aquarium. Daily variances in chemical, physical and biological phenomena are a fact of life in aquaria, linked to the light and dark cycles and the diurnal rhythms of captive aquatic systems. As one example, the pH of aquarium water typically peaks after the lights have been on all day at a maximum of perhaps 8.4, only to drop to low of below 8.0 overnight. This is related to photosynthesis and the fact that zooanthellae and green plants consume CO2 and produce O2 when there is adequate light, but in essence reverse that process in the dark, consuming O2 and giving off CO2. Redox levels, available calcium and other water quality parameters are affected in similar ways. Needless to say, these variations are far greater is a small, closed-system aquarium than they are in the ocean, so it’s beneficial to minimize such fluctuations by reversing the photoperiod in the main display and the sump/refugium. This is easily accomplished by timing the lighting in the sump so that the bed of macroalgae is illuminated after dark when the lights on the display tank are off, and vice versa. Just use alternating timers on the main tank and the sump/refugium tank so that when one is on, the other is off. (Other macroalgae require a period of darkness in order to thrive, but if you will be using Caulerpa, it can even be illuminated 24 hours a day around the clock in order to accomplish the same thing.) Voila! Just like that the roller coaster ride is over: no more daily fluctuations in pH or highs and lows in calcium levels, oxygen minima, or peaks and valleys in redox potential.

Continuously operating an efficient fluorescent tube or two shouldn’t cost much and will help prevent even the fastest growing Caulerpa from going sexual. Aside from assorted Caulerpa, Chaetomorpha and various species of Gracilaria or Ogo and Chaetomorpha spaghetti algae are other macros that would grow well in such a sump, although they would need a period of darkness to thrive and should therefore be maintained on a reverse photoperiod to the main tank.

Best of luck with the final preparations for your innovative aquarium system, Clintos!

Pete Giwojna

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