@nnero66466
This is only common things used, there are endless combinations so don't consider this as a complete list.
I copied some descriptions from bulk reef supply site [easier than typing it all out myself], I tried to condense it down to useful yet revelant information. Feel free to dive as deep as you want. By searching them for yourself.
So as far as what can go under filter pad in the media tower.
People typically run some type or combination of activated carbon. (GFO) Granular Ferric Oxde, purigen, or some all in one type products (chemipure elite/ chemipure blue).
***There are other more experienced reefers who know what they are doing that do other things, yet this is approiate for newer or casual reefers.***
Activated Carbon:
is great for a whole variety of reasons, ranging for removal of general contaminants, dissolved organics, undesirable odors, yellowing pigments in the water, removing the build-up of toxins that corals and algae emit to fight each other, and much more.
(GFO) Granular Ferric Oxide
(The amount of time GFO lasts depends on the phosphate levels in the aquarium. When first used, the first batch of GFO can exhaust quickly, usually within 1–2 weeks, due to high phosphate levels. After the first batch, subsequent batches can last 4–8 weeks, depending on the phosphate input.)
Gfo is the most widely used filter media in reef tanks. GFO is one of the best solutions for rising phosphate(P04) levels in a reef aquarium.
Phosphate battles are extremely common for reef tank owners, especially during those first couple of years when you are working to dial in your husbandry skills and establish biodiversity in the tank. Phosphate is a necessary and natural part of your reef tank, 99% of phosphate comes from fish food and the resulting waste. Lack of proper maintenance or poor quality source water can also contribute to phosphate stacking up in your tank. Your fish and corals both require phosphate to thrive but it's all about balance. Too much phosphate can begin to poison your coral, inhibiting their calcification and growth as well as contribute to unsightly nuisance algae outbreaks.
purigen: (lasts UP TO 6 months)
is used to control ammonia, nitrite, and nitrate levels. If you're struggling to get your aquarium's ammonia, nitrite, or nitrate levels under control, you'll want to go with Purigen.
For best results, Purigen should be placed so as to maximize the flow of water through it. It may be used in a canister filter, media chamber, box filter, or any high flow area of a trickle filter.
Chemi-Pure: (lasts 2-4 months)
is a chemical filtration media for aquariums that contains various materials, depending on the formula:
1.) Chemi-pure Elite
This formula contains pelletized carbon, ion-exchange resins, and granulated ferric oxide (GFO). It can help keep pH levels stable and is good for aquariums with medium bio-loads or high phosphate levels.
2.) Chemi-pure Blue
This formula contains pelletized activated carbon, ion resins, and an organic scavenger resin. It can help reduce organic compounds, odors, toxins, and phosphates, and can raise redox levels. It's designed to work in higher pH environments, such as marine reef jellyfish aquariums and tropical freshwater aquariums.
What i personally run in my media towers.
1.) Activated carbon- always
View attachment 59807
AquaClear 70 Activated Carbon Inserts, Aquarium Filter Replacement Media, 3-Pack, A1386 , White
https://a.co/d/6J3LH5s
This is cheap for me 3 for under $5 i order two at a time due to price. Just rinse and suspended in one of the media basket sections. I personally change this once a month or if anything looks odd in one of my tanks.
2.) Rowaphos (GFO) - always
View attachment 59808
Rowaphos 100 ml
https://a.co/d/ie45jpH
I change this roughly every other month, or when I notice po4 starting to rise in testing results. Not the cheapest but very effective in my tank.
3.) Purigen- 75% of the time.
View attachment 59818
Seachem Indoor Purigen Organic Filtration Resin - Fresh and Saltwater 100 ml
https://a.co/d/1Ablkt3
I change this about every 4 months.
* I use to run Chemi-pure, blue or elite. I found Rowaphos worked better at lowering my phosphates (po4)
View attachment 59810
View attachment 59811
Boyd Enterprises Chemi-Pure Aquarium Filtration Media, 5.5-Ounce, Blue
https://a.co/d/jm0W3qA
View attachment 59813
View attachment 59814
Boyd Enterprises ABE16743 Chemipure Elite for Aquarium, 11.74-Ounce
https://a.co/d/fcTjgUf
One are the other of these are a decent option, if you don't have lots of fish, corals, or feed heavy. They containna little of all mentioned above.
This would be changed 1-2 times a month for maximum effectivness.
Personal I found the individual elements more effective long term as my tank matured. For the first year and a half i ran only chemipure.
As far as placement in the media tower I do this.
Filter floss
Flat
(All water passes through this first)
Rowaphos
(Woven through the shelf above it so it hangs and doesn't restrict flow)
Purigen
(Zip tied suspended to shelf under Rowaphos)
Carbon
(Ziptied suspended to tbe shelf under the carbon. )
View attachment 59817
Zip Ties Assorted Sizes(4”+6”+8”+12”), 400 Pack, Black Cable Ties, UV Resistant Wire Ties by ANOSON
https://a.co/d/8bNARdd
I bought this pack of zip ties, they last forever and are useful for just about everything.