Is RO really necessary for Apistogramma baenschi, or can I make this work without it?

[Ada24]

Hi everyone,

I’m planning a new 80 × 35 × 45 cm (125 L / 33 gal) South American blackwater biotope aquarium and would really appreciate some advice before I commit to a species.

For a bit of background, this won’t be my first aquarium. I already run a healthy, established community tank and have experience keeping fish, maintaining water quality, and caring for more demanding species. However, this will be my first dedicated soft-water/blackwater aquarium, and I’ve never used a true RO system before.

The aquarium itself is established, and I’ll be taking it over together with its filter. The filter has been running for about 1.5 years in an aquarium with a pH of around 7.5, so I’d rather not shock the biological filtration by suddenly switching it to extremely soft, acidic water.

My source water (filtered drinking water) is approximately:

• pH: 6.8–7.2
• GH: 7 dGH
• KH: ~5 dKH

Installing a home RO system would be very difficult, and buying RO water from a fish store for every water change isn’t really practical.

The aquarium will have fine sand, lots of driftwood, leaf litter, botanicals, caves, visual barriers, and South American plants. The water will be tea-colored blackwater.

Planned stocking:

• 13 × Nannostomus marginatus
• 1 × L134 (Peckoltia compta)
• 1 × Red Lizard Whiptail or normal whiptail
• 1 pair (or trio, depending on species) of Apistogramma

My first choice is actually Apistogramma baenschi. If it’s realistically possible to keep them healthy and comfortable under my conditions, I’d much rather start with them from day one.

However, if my water chemistry simply isn’t suitable without RO, I’m considering starting with either:

• Apistogramma cacatuoides (probably a trio), or
• Apistogramma trifasciata

to gain experience with Apistos while the aquarium matures and I learn more about soft-water chemistry. If I eventually find a nice pair of baenschi and can improve my water preparation, I’d likely rehome the first Apistos and transition the tank to baenschi gradually.

I’m not trying to build a breeding setup. My main goal is to observe natural behavior, and if a few fry occasionally survive in the display tank, that would simply be a bonus.

My questions are:

• Is GH 7 / KH 5 simply too hard for captive-bred baenschi, even if the pH can be lowered?
• Is there a realistic and stable way to prepare water several days before water changes using botanicals, peat, acid buffers, or similar methods without using RO, or is RO essentially unavoidable for baenschi?
• Would trifasciata be a better intermediate choice than cacatuoides considering my current water parameters?
• If you were in my position, would you start with baenschi anyway, or would you gain experience with cacatuoides/trifasciata first and transition to baenschi later?

I’d especially appreciate hearing from people who have actually kept or bred A. baenschi, A. trifasciata, or A. cacatuoides under similar water conditions without a home RO system.