Suggestions For Bottom Feeder?

Hi, does anyone have any suggestions on which Bottom Feeders to buy for my tank please?

Tank is 100L, Sand Substrate, PH 7.2 Hard Water, got 2 Java Fern on Bogwood, stocked with 6 Glowlight Tetras and 6 Black Neon Tetras. Will also be stocking some Endlers soon too.

Any help would be appreciated very much.
Thank You.

You may have several options, but first I'd like to know the number of the water hardness.  A pH of 7.2 is not at all high, so I am wondering if your "hard" water may not actually be all that hard.  The GH (general hardness) is what I'm after, and this you can ascertain from your municipal water authority, likely on their website, unless you already have the number.
 
Byron.

We rang our local water supplier on Friday and had 2 different answers as to where our water came from. One source was an Underground Aquifer and the other was a local reservoir. If you go by the Underground Aquifer PH level 6.5-7, I think the GH was slightly hard 100-150. The reservoir water PH level 7.5-7.8 with hard water 210. Our PH reading when we had it tested on Friday was 7.2 so it was between the two PH levels.

PandorasPool said:

We rang our local water supplier on Friday and had 2 different answers as to where our water came from. One source was an Underground Aquifer and the other was a local reservoir. If you go by the Underground Aquifer PH level 6.5-7, I think the GH was slightly hard 100-150. The reservoir water PH level 7.5-7.8 with hard water 210. Our PH reading when we had it tested on Friday was 7.2 so it was between the two PH levels.

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Thanks.  That is not bad at all; the lower numbers are soft, the highest only moderately hard.  So you have a good selection.  I'll stay with South American in keeping with your present fish.  Many aquarists are very fond of the cory cats, and a group of 7-9 of any of the medium sized species (which is all but the three dwarfs, and excluding the very large species that are technically now in Scleromystax) would be fine.  The more the better as these are highly social fish.  
 
Among the more unusual, there is the common Whiptail (Rineloricaria parva, some use the genus Hemiloricaria though this is still in doubt and has not yet been fully accepted), just avoid the "giants" in other genera commonly referred to as "Royal."  There is also a very interesting reddish-brown form of R. parva, commonly called Red Lizard, that is also peaceful.  You can have either of these as one, or two or three.  They attain 5-6 inches but are so thin they do not appear "large" and suit smaller tanks like your 100 litre very well.  Will be fine with the corys, I have all of these together.
 
Byron.

Another option are kuhli loaches, you won't see them anywheres as often as corydoras and the like but they are super neat when you do see them.
I have a few and now see them on a bi weekly basis when I feed them.

 
Another option are kuhli loaches,

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I have 3 they are cool, I am starting to see mine more often now they have settled in a bit.