The one that got away.

The Weather Loach will also need to go back. These fish get to 10" or so and over an inch across. They shouldn't be kept in anything under 4' long, or in groups of less than 3 (and ideally more).

My advice would be to return all the fish, buy yourself a liquid test kit (the API Freshwater Master Kit, or the utrafin/Tetra equivalent are the ones most people use), a bottle of ammonia and start again with a fishless cycle.

Heaters for a 65L tank are not expensive and will give you a wide range of fish suitable for a tank the size you have. Exactly which fish will thrive will depend on how acidic/alkaline and hard/sot your water is (guppies love the liquid rock you get in London and the South East, whereas tetras like soft acidic water more usually found in Scotland). Hillstream Loaches would make good tankmates for WCMMs (although I'd be looking at putting them in a tank with an external filter just to keep the flow up for them. They shouldn't be put in immature tanks either, as they need a good supply of algae to graze on (a production line of pet rocks is a good idea).

Having said that there are a few species that would be suitable- White Cloud Mountain Minnows are pretty much ubiquitous and absolutely lovely fish. In terms of stocking level a good rule of thumb for small shoaling fish is 1cm of adult fish for every 2 litres of water volume, so a 65L tank would hold about 8-10 WCMMs (they get to 4cm each).

Take a bit of the goldfish filter out and swap it with the filter for the betta tank. The bacteria will gradually spread to the new media over a couple of weeks (as you've culled some of their population). Using this as a starting colony you can then put it in the new tank and start adding ammonia. You may find you get an "instant cycle" that way, but it isn't guarantee, so I'd test it out with ammonia rather than fish obviously. You'll certainly reduce your cycling time.

The sponge filter needs an air pump to work. the pump forces air though the sponge pullin water with it and circulating the water over the bacteria living on the sponge. They're very popular with betta keepers as they don't create much water movement. Shrimp keepers like them too, as the shrimp will pick morsels of food off them. (Whether you can keep shrimp and bettas together depends on the personality of the betta.)

No fish "clean" the tank. "Butterfly Plecs" are actually hillstream loaches and have very specialist requirements. They need well-oxygenated, clean, cool, fast-flowing water, and are therefore unsuitable tankmates for guppies (the long tails makes them poor swimmers, and they won't like the cold temperatures the loaches need), and a 35L tank is too small for them. They feed on the various micro-organisms that live in algae, and to do best will need to be in a tank with a supply of algae covered pebbles (you may need to set up a "pet rock production line" on a windowsill to supply them with the food they need).

If you want something to get rid of the algae on the tank glass you're better off either doing it yourself with an algae magnet, or the "razorblade on a stick" that Algarde do. If you must have an animal to do it for you, then Nerite Snails would be a much better option in a small tank.

If you want to keep mollies you'll need to use the heater, and keep the tank at around 26 degrees. The gold barbs don't necessarily need to be kept that warm, and as long as your house is not too cold will be happy with a tank at "room temperature" with some seasonal fluctuations. Mollies won't cope at all well with that.

So if you let your water mature for 24 hours (so you don't get pH fluctuations when doing water changes) you'll have to heat the water before adding it to the tank, so you don't shock the fish with a sudden temperature change. If you just kept the barbs then that isn't necessary as the water in the tank is going to be about the same temperature as the water in the bucket.

(Personally unless you can find "wild type" mollies- which sadly you probably can't- I wouldn't keep them at all, but then I'm not a fan of most artifical varieties of fish- especially the "balloon" ones.)

In a 100L tank a shoal of 7-10 gold barbs would put you about fully stocked based on the 1cm/2L "rule", which is more of a guideline really. Understocking a tank is never a bad idea when you're just starting out. When the tank is nice and mature and you have a good growth of algae you could get a Bristlnose Plec would be a nice addition, an give some interest at the bottom of the tank. (I'd have a heater set to about 20-21 degrees C if you got one, to keep the edge off just in case you had a cold snap. You'll probably find it only switches on on the very coldest nights).

If you do keep a couple of mollies get either only males or virgin females, or you'll very quickly have hordes of babies. (Females can store sperm for up to 3 months, and drop dozens of babies in one go). They're not shoaling species like the barbs are, so you don't *need* 6+ to keep them happy.

If you just keep gold barbs then you won't need to heat the water, as they like temperatures around 18-24 degrees C, so your aged, dechlorinated water at room temperature should be fine.

You won't be able to keep mollies with them however, as they like it warmer, and will need their water warmed up.

Given you've got the powerheads I'd go for a riverine set-up. Chaetostoma, hillstream loaches, darters, shiners, gobies. There's all sorts of fish that would love the current you can supply.

Blue-Finned Killies Lucania goodei are less aggressive than American Flag Fish, and are found in similar habitats, and there are a couple of brackish/marine US natives (the "Rainwater Killie" won't tolerate rainwater, and likes it salty! Just goes to show how useless common names are).

The only problem is that those and the AFFs are not true tropicals but will much prefer a tank that changes temperature with the seasons - its one reason why AFFs are aggressive, in a tropical tank its summer all the time and they're constantly in breeding mode. Mine are defintely much more relaxed now its a bit cooler.

That's great sounding tank- although perhaps unusual for a marine- most of the ones I see advertised are deep rather than wide. 3'x 5' gives you lots of options for bottom dwellers like catfish, loaches, dwarf snakeheads (if you like predatory thingies), etc. I take it you have an RO unit? If so I can't really advise on stocking other that to pick whatever you feel like.

Although I'd put a strong case for a nice biotope. Perhaps one that didn't involve a heater. ;) I think even the smaller gars are going to be too big- they're not particularly manoeverable. The heavy scales make them bad at turning corners. Beautiful fish though.

I took the vac end off the one I had and bought a Marina Siphon Start (the biorb one comes with a bulb at the end which is handy). I startt the siphon off, swirl the tube around above the sand and the grot that sits on the top gets sucked up. Any sand that gets sucked up gets sieved back into the tank with the new water, which means I can pull out MTS's and move them around to other tanks if I need to.