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under gravel filtration?

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    I’m going to set up my 5 gallon tank to hold a trio of fundulopanchax gardneri. The tank has an under gravel filter powered by a power head which leads into a chamber that i filled up with mechanical and chemical media? Will it be any good? Should i use my power filter instead?

    I was thinking of not using any sand or gravel but just some kind of soil like Nutra soil or Aqua soil. Will the chemical filtration suck up all the nutrients?

    I tested my water today and found it had an alarming pH value of 8. How can i lower it? I know i could use RO water, but i really don’t understand how it works and i don’t want to use anything i don’t understand in my tank. Can someone explain?

    I would like to plant it with a big clump of java fern on a root, some kind of low floating plant(the tank is covered), maybe some crypts, and there is a very slim chance of me maybe having a moss wall. What would you suggest as a floating plant, and what lighting should i use? 

    Tank measurements:

    Height: 30cm

    Length: 30cm

    Width: 23cm

    Water parameters:

    pH: 8

    I’ll test pH (again), GH and KH tomorrow at my LFS so i’m sure i don’t make any mistakes.

    My LFS can supply RO water

    Any suggestions?



    Hi George,


    RO water is the best way to reduce kH and GH, not necessarily pH. High pH is generally associated with a higher level of dissolved minerals. pH can be reduced to with RO but it is really because you are reducing the dissolved minerals and reducing the buffering capacity of the water. In simple terms, RO is just water where the minerals and other things have been removed/filtered out. 


    The fish you plan to keep aren’t particularly sensitive and should do okay if acclimated well. One way to reduce pH without using RO is to introduce organic acids like humic acid and tannins. Using peat in the filter or adding indian almond leaves are a couple options, but this will stain the water a tea color and will be removed by any chemical filtration thus negating the benefit. Again, I don’t think it is necessary to keep those fish. Your tap is probably just fine. If you use aquasoil that will buffer the water to a lower pH anyways. 


    From my understanding getting too hung up on pH isn’t the best practice. It is more about what does the pH represent. Are there a lot of basic ions in the water(high pH related to a lot of carbonates)? Are there a lot of acids? Is it too much CO2 (if using pressurized CO2 for plants)? These things become the real factors and can be indirectly measured by pH. 


    What type of chemical media are you using? Carbon will sequester organic material, not necessarily inorganic nutrients utilized by plants like nitrate, phosphate, and potassium. It can sequester some chelating agents used to bind trace elements so they dissolve. For most planted tanks carbon filtration is not necessary. If you plan to have plants I would not use anything like a phosphate or nitrate remover, even if you don’t I wouldn’t worry about it too much. Good husbandry like regular water changes and good biofiltration will take care of most things. A good amount of biofiltration is always a good idea. I’m not a big fan of UGFs. Kind of a PITA if you ask me. A gentle hang on the back filter (HOB) or in tank filter would be just fine. Those fish don’t like a ton of flow. 


    For the plants you listed you will not need much light, especially for that small of a tank. You could find a cheap small LED on ebay for your purposes. You want low light to avoid algae and stress to your fish since your focus is a few low light plants and the fish. 


    Best of luck,





    Thanks for the advice shawn. I have one more question though. 

    Can I use any soil, or is there a certain kind of soil i have to use considering i don’t want to cover it with sand gravel?



    You are welcome, George.


    If you plant crypts they would appreciate a nutrient rich soil. ADA aquasoil being one of the best, but also some of the most expensive. Seachem fluorite could be another option.


    The idea is to have a soil with a good CEC (cation exchange capacity). This means it will be able to hold and release nutrients to the plants. Plants with roots are particularly well adapted to capturing nutrients from these types of soils. Most baked clay soils have this capability. Sands and gravels do not, they are inert. Akadama is a pretty cheap option as well. It is a bonsai soil with a decent CEC, but has a tendency to break down and compact over time from what I’ve heard. I’ve used almost exclusively aquasoil and have been very happy with it.


    Your mosses and ferns do not care about the soil. Since your tank will be low on nutrient demand they would only need a little bit of fertilizing to the water column. Most any comprehensive store brand would be able to provide what would be needed.


    Root tabs under your crypts is a good idea, they will thank you for it.

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