You realize fish grow, right? A 10 cm RTC turns into a 15 cm RTC in a couple weeks and then 30 cm and eventually over 1 m. If you don't have a plan for a HUGE tank for that RTC within the next 6 months to a year, there is definitely a problem
Ain't you the joker who asked for HELP on what type of fish to keep in your 70g. An RTC, silver arowana or a channa. And despite all odds of ppl saying that rtc and arowana is way too small for a 70g you still got in anyway?
Yeah making a pond will go a long way in housing them. You have choosen two fish that require a large swimming space. They are definetley in the top ten percent of tank requirement size. esp the almost un housable rtc