I have counted around 25 of them and they currently reside in a 20 gallon tank.
1	I	I	PRON	PRP	Case=Nom|Number=Sing|Person=1|PronType=Prs	3	nsubj	3:nsubj	_
2	have	have	AUX	VBP	Mood=Ind|Number=Sing|Person=1|Tense=Pres|VerbForm=Fin	3	aux	3:aux	_
3	counted	count	VERB	VBN	Tense=Past|VerbForm=Part	0	root	0:root	_
4	around	around	ADV	RB	_	5	advmod	5:advmod	_
5	25	25	NUM	CD	NumForm=Digit|NumType=Card	3	obj	3:obj	_
6	of	of	ADP	IN	_	7	case	7:case	_
7	them	they	PRON	PRP	Case=Acc|Number=Plur|Person=3|PronType=Prs	5	nmod	5:nmod:of	_
8	and	and	CCONJ	CC	_	11	cc	11:cc	_
9	they	they	PRON	PRP	Case=Nom|Number=Plur|Person=3|PronType=Prs	11	nsubj	11:nsubj	_
10	currently	currently	ADV	RB	_	11	advmod	11:advmod	_
11	reside	reside	VERB	VBP	Mood=Ind|Number=Plur|Person=3|Tense=Pres|VerbForm=Fin	3	conj	3:conj:and	_
12	in	in	ADP	IN	_	16	case	16:case	_
13	a	a	DET	DT	Definite=Ind|PronType=Art	16	det	16:det	_
14	20	20	NUM	CD	NumForm=Digit|NumType=Card	15	nummod	15:nummod	_
15	gallon	gallon	NOUN	NN	Number=Sing	16	compound	16:compound	_
16	tank	tank	NOUN	NN	Number=Sing	11	obl	11:obl:in	SpaceAfter=No
17	.	.	PUNCT	.	_	3	punct	3:punct	_
