I am not familiar with the Fluval Evo 5-gallon aquarium system, sir, so I cannot advise you from my own personal experience regarding that particular tank.
However, if you are able to manage the water flow so that it will not be too overpowering for the pigmy ponies and will not filter out all of the live foods before the dwarf seahorses have a chance to eat it, it might be suitable.
I usually accomplish that with the use of simple air-operated foam filters in a dwarf seahorse tank, rather than any sort of power filters, so I am not sure what would work in your case in order to screen off the intakes for the power filters. Plastic window screen would certainly make it safe for the dwarf ponies but would probably not prevent baby brine shrimp or copepods from being sucked into the filtration system…
Personally, for a dwarf seahorse tank I would suggest setting up a five-to 10-gallon aquarium equipped with a fluorescent light fixture and simple, foolproof sponge filters. For best results, keep the aquarium well planted with lush beds of macroalgae, as discussed below.
The sponge filters I find that work well are the Oxygen Plus Bio-Filters (models 2, 3, 4, or 5) or the Tetra Brilliant foam filters. They have no metal components, making them completely safe for use in saltwater, and just one of these foam filters will do the job on a tank of 5 gallons or less. They do not have a weighted bottom. They have suction cups to anchor them in place instead.
The following foam filter will work great for a 5-10 gallon setup:
Avoid the Oxygen Plus Bio-filter 6, 11, and the Multi sponge, which all have a weighted bottom (metal), that rusts when exposed to saltwater. Sooner or later this will cause problems in a marine aquarium (sooner in the small setups that are most suitable for dwarf seahorses). If you want more filtration, you’re better off going with two of the smaller suction cup sponge filters rather than any of the models with weighted bottoms. For instance, for a 10-gallon tank, I’d suggest using two well-established foam filters, one at either end of the tank for the biofiltration.
All you need to operate sponge or foam filters is an inexpensive, diaphragm-operated air pump (whatever is available at a reasonable price from your LFS will do just fine), a length of airline tubing to connect the air pump to the foam filter(s), and a set of air valves (gang valves) to regulate the air flow to the filters. That’s all — nothing to it!
Cleaning the foam filters is a snap. Simply immerse them in a bucket of saltwater and gently squeeze out the sponge until it’s clean and releases no more sediment or debris. Run a bottlebrush through the inside of the tube, wipe off the outside of the tube, and you’re done. The filter is ready to go back in the aquarium with no impairment at all of the biofiltration. Takes only a couple minutes.
For the substrate with sponge filters, I like a bed of black sand about 3/4-inch to 1-inch deep, both for it’s pleasing appearance and to accommodate Nassarius snails, which like to bury in the sand bed.
For small setups like this, I recommend performing small weekly or biweekly water changes of 10%-15%, rather than the monthly or bimonthly water changes I perform on large setups, but the volume of the water exchanged is so small — just a gallon or so at most — that they are a breeze. Heck, if I mix up a 5-gallon bucket of new artificial salt mix in advance, that provides enough clean, aged saltwater for a month’s worth of water changes on my dwarf tank. When I siphon out the water for the weekly exchanges, I use the opportunity to vacuum the substrate and tidy up the tank a bit. Once it settles, I use the water I siphoned out to clean the sponge filters. The whole process, water change and all, takes all of 10 minutes.
But that 10 minutes of weekly maintenance returns wonderful rewards in terms of water quality. With such a small volume of water, the conditions can deteriorate quickly in a dwarf tank, and this modicum of weekly maintenance keeps things running smooth and trouble free.
For decorating or aquascaping a dwarf seahorse tank, Doug, I suggest using one or more seahorse trees along with lush beds of macroalgae. Caulerpa mexicana is ideal for this, but any of the various long-bladed and plumed or feathery varieties such as Caulerpa sertularioides, Caulerpa ashmedii, Caulerpa serrulata and Caulerpa prolifera would work just as well. To go with the Caulerpa, I like to use red and gold species of Gracilaria (Hawaiian Ogo), which go great with the bright green of the Caulerpa. The result is a colorful macroalgae garden with a very nice contrast of colors (reds, yellows, greens, and brown) and interesting shapes. A tank heavily planted with macros such as these is a lovely sight and mimics the dwarf seahorse’s natural seagrass habitat well.
If you cannot get the Caulerpa (it’s illegal in some coastal areas) or you prefer the convenience of artificial plants, you can accomplish the same affect by using lifelike artificial aquarium plants that are safe for use in saltwater.
In addition, I will send you a document that includes comprehensive information regarding other hobbyists preferred dwarf setups, which will also explain how to control hydroids using fenbendazole, as an attachment to an email so that you can download the attachment, save it on your computer, and read through the information at your convenience, Doug. This document will also discuss some of the live foods that are useful for feeding dwarf seahorses other than newly hatched brine shrimp.
Best of luck with your plans for a dwarf seahorse tank, Doug!
Pete Giwojna, Ocean Rider Tech Support