Major temp issues in the 3.7

[Fatjim]

So I have a 3.7 reef next to a window (only spot unfortunately) I have the window covered to prevent light, however it obviously is still letting drafts/heat in.
So during the winter I was running an auto 50 watt heater bc of how cold it was and it did fine.
As it started to warm up I was getting random spikes of 89° so I down graded to a 25watt. Things went well for a bit but i was still getting high temp spikes so I again down graded to I believe a 5watt (rated for up to 5g) and for the second time this week I got readings of 68°!!!
Generally the lows and highs correspond with inside and outside temp changes (cold in the morning) and typically it fixes itself by noon however it's 7pm and I'm reading 68.9 Idk if the heater **** the bed but I'll be replacing it no matter what but I have no idea to what exactly.


Any and all input is highly appreciated

Heres a pic of the tank and my very upset coral
:stocking
Asst zoas/plays
Gsp
Xenia
Hammer
Flower nem
Florida rics
Toad stool

Fire shrimp
Nem crab
Pistol/goby
Hermits
Bumblebee snails
Pom pom crab
Sexy shrimp
And "lil homie nemo"

Fluval nano led light

 

[LiveWire]

You should heat your water at 3 watts per gallon. You may want to think about getting a controller as well like an Apex Jr. You can also set up a dual heater system so that you can use two smaller heaters rather than just one and set the temp a few degrees apart so they work together.

With a controller you could program a fan to come on and blow over the tank if it gets too hot in the summer as well. I would recommend replacing your heaters once a year also. I normally change mine out on Jan 2nd.

 

[Copingwithpods]

You shouldn't need to downgrade your heater as interior/exterior temperature rises, put the 50w back in it and as long as it's set to your target temperature just leave it be.

You have a cooling problem not a heating problem. The heating problem was created by you when you downgraded the heater.

 

[Fatjim]

Gotcha, now the 50watt I have is a pre set, is that fine or should I opt for an adjustable

 

[Copingwithpods]

Gotcha, now the 50watt I have is a pre set, is that fine or should I opt for an adjustable

I'm guessing it's preset to 78ish?

Its OK per say but it depends on alot of things. The most important being that it actually shuts off at 78.

My house heats up quiet a bit and because my heater is adjustable in the summer I bring my temperature up from 77 to 79 to minimize temperature swings. My fans can keep the tank under 80 but cannot bring it all the way down to 77, specially mid day. If your heater was adjustable you could bring it up to 79-80 and reduce those huge swings.

Now you mentioned 89 degrees which is of real concern and must be addressed by either moving the tank away from the window or by an inexpensive temperature controller hooked up to a fan. A fairly decent 80mm fan should keep your small tank under 80 degrees fairly easily.