All of the photos are from outside of the tank. The majority of the photos are taken in the tank the fish resides, but I do have a handful of special photo tanks that I use for photos. Tank sizes vary from one half gallon up to 20 gallons. I just had a half gallon tank made with Sapphire glass that I take with me in my luggage when I travel to take photos.
I have several cameras. All of them are Njkon. My workhorse is a Nikon D810 but I also have a D800, D700 and a D4. The key is the lighting. I use up to four Nikon speed lights to light the tank. All of the light give me an opportunity to select settings that assure clarity, color, contrast, etc. it also allows me to achieve that darker background effect.
That article was printed in both Tropical Fish Hobbyist and Amazonas magazine. I don't have the link, but you might be able to search their on line archive. Look at Amazonas's Reef to Rainforest site. It was about breeding Managuense.
With most of the variants, the differences can be subtle...size, color, pattern. With these, there's not much from your run of the mill Managuense. The Honduran variant was unique in having a blue sheen along their spine.I wasn't on the collection trip, but apparently a group that went to the Mosquito Coast in Mexico collected a fish that had a green coloration. If memory serves, they weren't able to bring it back alive.
Thanks for the props. I strive to approach aquatic photography the same way I approach fine art photos. With an eye on composition and interest. Having an understanding of the fish behavior is a plus. Having access to the fish is also a plus.