What are the symptoms ?
My aquarium water heats up to 29'c during the day , i guess most of the plants are not too happy about that..
Which plants don't like higher temp? ...discus owners will know i suppose..
It's 110F here most summers, sometimes more, not many places get that hot.
I rarely use AC, so .........plant growth rates increase, Metabolism is faster as you increase temps, most aquatic plants are fine to about 40C.
Warmer water needs more current to cool it off and also more CO2/O2.
You have a nice tank; we do not see anything that should have too difficult a time with the heat.
We recommend you open the top; perhaps even lift (raise) the top, if you can place or direct a fan to blow air across the water helps.
The less humid the air the more evaporative cooling you will have.
We have yet to have the opportunity to visit Primorsko-Goranska Zupanija, but our guess is that Krk is humid, warm Mediterranean, so we doubt you will have too many problems.
We have just had our first blast of 43 C plus weather; it is still dry so the outdoor fish tanks have not exceeded 30 C yet. As the Monsoon, advances the humidity will raise and eventually the smaller tanks will run temperatures as high as 35.5-36 C.
We move mosses and ferns inside and release some of the more sensitive fish into a pond or bring them inside.
Over the years, we have developed this routine that includes extra water changes, we used to add extra aeration, but I really have not done that the last couple of years. Give the plants time to adapt and if you are using a canister filter extra cleaning is in order.
The plants seem to adapt quite well and we see increased breeding with many of the fish.
you can use small fan to control the temp of tank, in general speaking it can make 2'c lower than your room temp. but it does not work when it is humidity. In China, we use the cooling machine for freshwater and marine.
To keep the temp of tank below 32'c, everthing could be fine...