Starting a 20 gallon. How many fish?

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May 25, 2010
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First off, I have a lot of experience with freshwater but none with marine. I built a 20 gallon with sand (not live) and a Marineland Penguin 200 filter (up to 50 gallon biowheel) with the other obvious things like heater, hydrometers, etc. I plan on getting maybe a pound or 2 of liverock too before I put any fish in. I'm wondering how many fish I could put in it over the next 6 months.

These are the ones I was shooting for:

1 Green Spotted Puffer (Ralph) - I already have him and the point of this tank was for him (right now he is about an inch and a half). He's extremely docile. He's always careful not to bump into other fish and looks offended if one bumps into him.

1 Scooter Blenny (the ones at my petco eat dead food, I watched them feed)

1 Ocellaris Clown Fish

1 Bar Goby


I'd get them in that order. I didn't think there was enough water for the goby, or maybe even the clown, but really want to get them if I could. Also, there are a ton of places for them to hide and cave in so that shouldn't be a problem.
 
SW is very different from FW so first I would recommend reading up as much as you can before you get started and then read some more :)

Personally I would not recommend the biowheel filters. Things like biowheels, bioballs and sponges that are used in FW get clogged up quickly with detritus in a SW tank and cause poor water quality conditions. Your main source of filtration in a SW tank is your lie rock and sand. Therefore, I would recommend investing in at least 15 lbs of quailty LR to add to your existing sand. I also don't recommend silica sand if that is what you have. You should use aragonite sand (does not need to be live).

In order for your LR to function properly you will also need good flow in the tank to push the water through the LR harboring the beneficial bacteria. Theoretically that's all you need in a nano size tank provided your bioload (mainly fish) is kept low. A small HOB filter (without biowheels) can also be used to house some mechanical filtration such as filter floss (should be changed out frequently), carbon, GFO, etc. The better option would be to add a protein skimmer and or a refugium, especially if you plan to stock the tank heavy with fish and or feed a lot. This is a pic of my tank using only LR, sand, powerheads and a small HOB filter that I clean out weekly. It's far from perfect but its healthy and I am very happy with it.

100_3688.jpg


I would not recommend the puffer or the blenny. The puffer is going to be aggressive and while the clown can likely hold it's own, the others likely will not. I am also not sure about those puffers in a full marine system. Aren't they more of a brackish water fish? In any case they are aggressive and in a small tank that usually means bad news. Regardless of whether the scooters at your Petco are eating prepared foods, odds are not in your favor to keep one in a tank that size long term. The clown and goby are good choices but some would say the clown will get too big as well. THere are so many fish you can choose from that would do well in your tank. If it were me I would look into no more than 3 small fish and some nice inverts. A goby/pistol shrimp combo would be a great fit and a lot of fun to watch.

Don't mean to discourage, just offering advice based on my experiences and readings. HTH
 
Ok I'll look into getting more rock then. Also, I'll just take the biowheel out I guess. GSP in marine actually do as well as or better than they do in high brackish. Figure 8s can't though. GSP usually are aggressive but this one isn't. Puffers are very individual fish. I orginally got 2 but had to be returned within an hour of feeding because it constantly nipped at him after and he wouldn't defend himself. I also have a separator that I can use temporarily to setup another tank or donate the blenny in case he does start to nip when he gets older. But as of now he leaves the corys he's with alone and there are gsp that do grow up staying docile. I'll rethink about the blenny for feeding reasons, I thought dragonets were ok if they at dead food already.
 
30g is the minimum for a GSP. Imagine a 6" Nerf football swimming in a 29g tank. If you want any tank mates, go with a 55g.
 
I forgot to mention this is more of a temporary tank. I've got 1 more year of college left and a 75 waiting in my parent's garage for when I get a place of my own (tank was $50 on craigslist including stand and lid and doesn't leak :thumbsup:). This is something to separate Ralph from the freshwater fish to get him on salt, but I want to have at least 1 tankmate because fish tend to become more aggressive when you keep them alone for long periods of time (at least puffers from what I've heard).
 
Just an update. I just picked up a 37 on craigslist that was a good deal. I'm going to put the sand and water in it from the 20 that's been running for a week. I'm still going to stick with the same 4 fish, and it will still not be the "adult tank" for my gsp.
 
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