Old school reef keeping Yes, It is possible to keep reef tank without sump and chiller! However, u had to understand the concept of reef keeping and limited to hardy corals. IMO, Heat is the main concern. There are few things had to be in control in your tank. 1. Ammonia, Nitrate and Phosphate: use only biological filter, like "CURED" LIVE rock or MarinePure inside tank. No electricity driven filtration to minimise heat. Minimise number of fish. 2. Heat: use appropriate number of fan to lower temperature. Too many fan is noisy and water evaporates to drastic. Check salinity frequently and refill evaporated water with rodi/distilled water. 3. Water movement: use appropriate size/number of DC wave maker. Too large or many wm produce heat to water. Wm is a must to help move water around live rock/marinepure for biological filtration 4. Light: may want to use low heat Led light, 5. Waste export: Use wooden airstone driven skimmer. No heat. You may want to hang a small basket of Cheato under the light for nutrient export. Hope my input help u start your first reef tank. [emoji4] And may one day become a true reefaholic [emoji14] Sent from my CPH1611 using Tapatalk